Oxygen
Scientific knowledge base
The cardiac and respiratory systems work together to supply the body with oxygen necessary for carrying out the respiratory and metabolic processes needed to sustain life. Blood is oxygenated through the mechanisms of ventilation, perfusion, and transport of respiratory gases. Neural and chemical regulators control the rate and depth of respiration in response to changing tissue oxygen demands. The cardiovascular system provides the transport mechanisms to distribute oxygen to cells and tissues of the body (McCance and Huether, 2019).
Respiratory physiology
Respiration is the exchange of oxygen and carbon dioxide during cellular metabolism. It is commonly confused with the act of air moving in and out of the lungs, which is actually ventilation. The airways of the lung transfer oxygen from the atmosphere to the alveoli and the alveolar capillary membrane, where respiratory gases, oxygen and carbon dioxide (CO2), are exchanged. There are three steps in the process of oxygenation: ventilation, perfusion, and diffusion (McCance and Huether, 2019).
Structure and function.
The respiratory muscles, pleural space, lungs, and alveoli are essential for ventilation, perfusion, and the exchange of respiratory gases. Gases move into and out of the lungs through pressure changes. Intrapleural pressure is negative, or less than atmospheric pressure, which is 760 mm Hg at sea level. For air to flow into the lungs, intrapleural pressure becomes more negative, setting up a pressure gradient between the atmosphere and the alveoli. The diaphragm and external intercostal muscles contract (move downward and outward) to create a negative pleural pressure and increase the size of the thorax for inspiration. Relaxation of the diaphragm and contraction of the internal intercostal muscles allow air to escape from the lungs (Cedar, 2018; McCance and Huether, 2019).
Ventilation is the process of moving gases into and out of the lungs, with air flowing into the lungs during inhalation (inspiration) and out of the lungs during exhalation (expiration). It requires coordination of the muscular and elastic properties of the lungs and thorax. The major inspiratory muscle of respiration is the diaphragm. It is innervated by the phrenic nerve, which exits the spinal cord at the fourth cervical vertebra. Perfusion relates to the ability of the cardiovascular system to pump oxygenated blood to the tissues and return deoxygenated blood to the lungs. Finally, diffusion is responsible for moving the respiratory gases from one area to another by concentration gradients. For the exchange of respiratory gases to occur, the organs, nerves, and muscles of respiration need to be intact, and the central nervous system needs to be able to regulate the respiratory cycle (Cedar, 2018; McCance and Huether, 2019).
Conditions or diseases that change the structure and function of the pulmonary system alter respiration. Some of these conditions include chronic obstructive pulmonary disease (COPD), asthma, lung cancer, and cystic fibrosis. In these conditions, patients may experience increased respiratory rate, decreased oxygen saturation levels, decreased lung expansion, or adventitious lung sounds (McCance and Huether, 2019).
Work of breathing.
Work of breathing (WOB) is the effort required to expand and contract the lungs. In the healthy individual breathing is quiet and accomplished with minimal effort. The amount of energy expended on breathing depends on the rate and depth of breathing, the ease in which the lungs can be expanded (compliance), and airway resistance (McCance and Huether, 2019).
Inspiration is an active process, stimulated by chemoreceptors, which monitor pH, PaCO2, and PaO2 in the blood. Expiration is a passive process that depends on the elastic recoil properties of the lungs, requiring little or no muscle work. Surfactant is a chemical produced in the lungs to maintain the surface tension of the alveoli and prevent them from collapsing. Patients with advanced COPD lose the elastic recoil of the lungs and thorax. As a result, the patient’s work of breathing increases. In addition, patients with certain pulmonary diseases have decreased surfactant production and sometimes develop atelectasis. Atelectasis is a collapse of the alveoli that prevents normal exchange of oxygen and carbon dioxide (McCance and Huether, 2019).
Accessory muscles of respiration (the intercostal muscles in the rib cage and abdominal muscles) can increase lung volume during inspiration. Patients with COPD, especially emphysema, frequently use these muscles to increase lung volume. Prolonged use of the accessory muscles does not promote effective ventilation and eventually causes fatigue. During assessment, a patient’s clavicles may elevate during inspiration, which can indicate ventilatory fatigue, air hunger, or decreased lung expansion (McCance and Huether, 2019).
Compliance is the ability of the lungs to distend or expand in response to increased intraalveolar pressure. Compliance decreases in diseases such as pulmonary edema, interstitial and pleural fibrosis, and congenital or traumatic structural abnormalities such as kyphosis or fractured ribs (McCance and Huether, 2019).
Airway resistance is the increase in pressure that occurs as the diameter of the airways decreases from mouth/nose to alveoli. Any further decrease in airway diameter by bronchoconstriction or the presence of excess mucus can increase airway resistance. Diseases causing airway obstruction, such as asthma, tracheal edema, or COPD, increase airway resistance. When airway resistance increases, the amount of oxygen delivered to the alveoli decreases (McCance and Huether, 2019).
Increased use of accessory muscles, decreased lung compliance, and increased airway resistance increase the WOB, resulting in increased energy expenditure. Therefore, the body increases its metabolic rate and the need for more oxygen. The need for elimination of carbon dioxide also increases. This sequence is a vicious cycle for a patient with impaired ventilation, causing further deterioration of respiratory status and the ability to oxygenate adequately (McCance and Huether, 2019).
Lung volumes.
The normal lung volumes are determined by age, gender, and height. Tidal volume is the amount of air exhaled following a normal inspiration. Residual volume is the amount of air left in the alveoli after a full expiration. Forced vital capacity is the maximum amount of air that can be removed from the lungs during forced expiration (McCance and Huether, 2019). Variations in tidal volume and other lung volumes are associated with alterations in patients’ health status or activity, such as pregnancy, exercise, obesity, or obstructive and restrictive conditions of the lungs.
Pulmonary circulation.
The primary function of pulmonary circulation is to move blood to and from the alveolar capillary membrane for gas exchange. Pulmonary circulation begins at the pulmonary artery, which receives poorly oxygenated mixed venous blood from the right ventricle. Blood flow through this system depends on the pumping ability of the right ventricle. The flow continues from the pulmonary artery through the pulmonary arterioles to the pulmonary capillaries, where blood comes in contact with the alveolar capillary membrane and the exchange of respiratory gases occurs. The oxygen-rich blood then circulates through the pulmonary venules and pulmonary veins, returning to the left atrium (McCance and Huether, 2019).
Respiratory gas exchange.
Diffusion is the process for the exchange of respiratory gases in the alveoli of the lungs and the capillaries of the body tissues. Diffusion of respiratory gases occurs at the alveolar capillary membrane (Fig. 41.1). The thickness of the membrane affects the rate of diffusion. Increased thickness of the membrane impedes diffusion because gases take longer to transfer across the membrane. Patients with pulmonary edema, pulmonary infiltrates, or pulmonary effusion have a thickened membrane, resulting in slow diffusion, slow exchange of respiratory gases, and decreased delivery of oxygen to tissues. Chronic diseases (e.g., emphysema), acute diseases (e.g., pneumothorax), and surgical processes (e.g., lobectomy) often alter the amount of alveolar capillary membrane surface area (McCance and Huether, 2019).
FIG. 41.1Alveoli at terminal end of lower airway.
Diagram shows cross-section of alveoli with labels for bronchiole, pulmonary arteriole, pulmonary venule, terminal bronchiole, alveolar sac, alveoli, and alveolar duct.
Source: (From Patton KT, Thibodeau GA: Human body in health and disease, ed 7, St Louis, 2018, Elsevier.)
Oxygen transport.
The oxygen-transport system consists of the lungs and cardiovascular system. Delivery depends on the amount of oxygen entering the lungs (ventilation), blood flow to the lungs and tissues (perfusion), rate of diffusion, and oxygen-carrying capacity. Three things influence the capacity of the blood to carry oxygen: the amount of dissolved oxygen in the plasma, the amount of hemoglobin, and the ability of hemoglobin to bind with oxygen. Hemoglobin, which is a carrier for oxygen and carbon dioxide, transports most oxygen (approximately 97%). The hemoglobin molecule combines with oxygen to form oxyhemoglobin. The formation of oxyhemoglobin is easily reversible, allowing hemoglobin and oxygen to dissociate (deoxyhemoglobin), which frees oxygen to enter tissues. Patients who are acidotic (pH less than 7.35; seen in patients with sepsis or diabetic ketoacidosis), hypercapnic (elevated PaCO2 levels; seen in patients with COPD), or who have low hemoglobin levels (seen in patients with anemia or excess blood loss) have decreased ability to carry oxygen and therefore to deliver oxygen to the tissues (McCance and Huether, 2019).
Carbon dioxide transport.
Carbon dioxide, a product of cellular metabolism, diffuses into red blood cells and is rapidly hydrated into carbonic acid (H2CO3). The carbonic acid then dissociates into hydrogen (H) and bicarbonate (HCO3-) ions. Hemoglobin buffers the hydrogen ion, and the HCO3- diffuses into the plasma. Reduced hemoglobin (deoxyhemoglobin) combines with carbon dioxide, and the venous blood transports the majority of carbon dioxide back to the lungs to be exhaled (McCance and Huether, 2019).
Regulation of ventilation.
Regulation of ventilation is necessary to ensure sufficient oxygen intake and carbon dioxide elimination to meet the demands of the body (e.g., during exercise, infection, or pregnancy). Neural and chemical regulators control the process of ventilation. Neural regulation includes the CNS control of respiratory rate, depth, and rhythm. The cerebral cortex regulates the voluntary control of respiration by delivering impulses to the respiratory motor neurons by way of the spinal cord. Chemical regulation maintains the appropriate rate and depth of respirations based on changes in the carbon dioxide (CO2), oxygen (O2), and hydrogen ion (H+) concentration (pH) in the blood. Changes in levels of O2, CO2, and H+ (pH) stimulate the chemoreceptors located in the medulla, aortic body, and carotid body, which in turn stimulate neural regulators to adjust the rate and depth of ventilation to maintain normal arterial blood gas levels (McCance and Huether, 2019).
Cardiovascular physiology
Cardiopulmonary physiology involves delivery of deoxygenated blood (blood high in carbon dioxide and low in oxygen) to the right side of the heart and then to the lungs, where it is oxygenated. Oxygenated blood (blood high in oxygen and low in carbon dioxide) then travels from the lungs to the left side of the heart and the tissues. The cardiac system delivers oxygen, nutrients, and other substances to the tissues and facilitates the removal of cellular metabolism waste products by way of blood flow through other body systems such as respiratory, digestive, and renal (McCance and Huether, 2019).
Structure and function.
The right ventricle pumps deoxygenated blood through the pulmonary circulation (Fig. 41.2). The left ventricle pumps oxygenated blood through the systemic circulation. As blood passes through the circulatory system, there is an exchange of respiratory gases, nutrients, and waste products between the blood and the tissues. Alterations in structure and function of the heart can lead to a variety of symptoms, including but not limited to dyspnea, edema, and weak pulses. Nurses hear abnormal heart sounds, such as murmurs or rubs, when the structure of the heart is altered (McCance and Huether, 2019).
FIG. 41.2Schematic representation of blood flow through the heart. Arrows indicate direction of flow and pulmonary circulation.
Cross-section of heart shows flow of blood inferior and superior vena cava entering into the right atrium, which further enters into pulmonary artery passing through right ventricle. Blood from left atrium enters pulmonary artery passing through left ventricle.
Source: (Modified from Harding MM et al: Lewis’s Medical-surgical nursing: assessment and management of clinical problems, ed 11, St Louis, 2020, Elsevier.)
Myocardial pump.
The pumping action of the heart is essential to oxygen delivery. There are four cardiac chambers: two atria and two ventricles. The ventricles fill with blood during diastole and empty during systole. The volume of blood ejected from the ventricles during systole is the stroke volume. Hemorrhage and dehydration cause a decrease in circulating blood volume and a decrease in stroke volume (McCance and Huether, 2019).
Myocardial fibers have contractile properties that allow them to stretch during cardiac filling. In a healthy heart this stretch is proportionally related to the strength of contraction. As the myocardium stretches, the strength of the subsequent contraction increases; this is known as the Frank-Starling (Starling’s) law of the heart. In the diseased heart (cardiomyopathy), Starling’s law does not apply because the increased stretch of the myocardium is beyond the physiological limits of the heart. The subsequent contractile response results in insufficient stroke volume, and blood begins to “back up” in the pulmonary (left heart failure) or systemic (right heart failure) circulation (McCance and Huether, 2019).
Myocardial blood flow.
To maintain adequate blood flow to the pulmonary and systemic circulation, myocardial blood flow must supply sufficient oxygen and nutrients to the myocardium itself. Blood flow through the heart is unidirectional. The four heart valves ensure this forward blood flow (see Fig. 41.2). During ventricular diastole the atrioventricular (mitral and tricuspid) valves open, and blood flows from the higher-pressure atria into the relaxed ventricles. As systole begins, ventricular pressure rises and the mitral and tricuspid valves close. Valve closure causes the first heart sound (S1) (McCance and Huether, 2019) (see Chapter 30).
During the systolic phase, the semilunar (aortic and pulmonic) valves open, and blood flows from the ventricles into the aorta and pulmonary artery. The mitral and tricuspid valves stay closed during systole, so all of the blood is moved forward into the pulmonary artery and aorta. As the ventricles empty, the ventricular pressures decrease, allowing closure of the aortic and pulmonic valves. Valve closure causes the second heart sound (S2). Some patients with valvular disease have backflow or regurgitation of blood through the incompetent valve, causing a murmur that you can hear on auscultation (McCance and Huether, 2019) (see Chapter 30).
Coronary artery circulation.
The coronary circulation is the branch of the systemic circulation that supplies the myocardium with oxygen and nutrients and removes waste. The coronary arteries fill during ventricular diastole. The left coronary artery has the most abundant blood supply and feeds the more muscular left ventricular myocardium, which does most of the work of the heart (McCance and Huether, 2019).
Systemic circulation.
The arteries of the systemic circulation deliver nutrients and oxygen to tissues, and the veins remove waste from tissues. Oxygenated blood flows from the left ventricle through the aorta and into large systemic arteries. These arteries branch into smaller arteries; then arterioles; and finally, the smallest vessels, the capillaries. The exchange of respiratory gases occurs at the capillary level, where the tissues are oxygenated. The waste products exit the capillary network through venules that join to form veins. These veins become larger and form the vena cava, which carry deoxygenated blood back to the right side of the heart, where it then returns to the pulmonary circulation (McCance and Huether, 2019).
Blood flow regulation.
The amount of blood ejected from the left ventricle each minute is the cardiac output. The normal cardiac output is 4 to 8 L/min in the healthy adult at rest. The circulating volume of blood changes according to the oxygen and metabolic needs of the body. For example, cardiac output increases during exercise, pregnancy, and fever but decreases during sleep. The following formula represents cardiac output:
Cardiac Output
=
Stroke Volume
(
SV
)
×
Heart Rate
(
HR
)
Stroke volume is the amount of blood ejected from the ventricle with each contraction. The normal range for a healthy adult is 50 to 75 mL per contraction. Preload, afterload, and myocardial contractility all affect stroke volume. Preload is the amount of blood in the left ventricle at the end of diastole before the next contraction. It is often referred to as end-diastolic volume. The ventricles stretch when filling with blood. The more stretch on the ventricular muscle, the greater the contraction and the greater the stroke volume (Starling’s law). In certain clinical situations, medical treatment alters preload and subsequent stroke volumes by changing the amount of circulating blood volume. For example, when treating a patient who is hemorrhaging, increased fluid therapy and replacement of blood increase circulating volume, thus increasing the preload and stroke volume, which in turn increases cardiac output. If volume is not replaced, preload, stroke volume, and the subsequent cardiac output decrease (McCance and Huether, 2019).
Afterload is the resistance to the ejection of blood from the left ventricle. The heart works harder to overcome the resistance so that blood can be ejected from the left ventricle. The diastolic aortic pressure is a good clinical measure of afterload. In hypertension, the afterload increases, causing an increase in cardiac workload (McCance and Huether, 2019).
Myocardial contractility is the ability of the heart to squeeze blood from the ventricles. It also affects stroke volume and cardiac output. Poor ventricular contraction decreases the amount of blood ejected. Injury to the myocardial muscle, such as an acute MI, causes a decrease in myocardial contractility (McCance and Huether, 2019). The myocardium in some older adults is stiffer with a slower ventricular filling rate and prolonged contraction time (Touhy and Jett, 2018).
Heart rate affects blood flow because of the relationship between heart rate and diastolic filling time. For example, a sustained heart rate greater than 160 beats/min decreases diastolic filling time, which decreases stroke volume and cardiac output (McCance and Huether, 2019). The heart rate of the older adult is slow to increase under stress, but studies have found that this may be caused more by lack of conditioning than age. Exercise is beneficial in maintaining function at any age (Touhy and Jett, 2018).
Conduction system.
The rhythmic relaxation and contraction of the atria and ventricles depend on continuous, organized transmission of electrical impulses. The cardiac conduction system generates and transmits these impulses (Fig. 41.3).
FIG. 41.3Conduction system of the heart. AV, Atrioventricular; SA, sinoatrial.
A) Diagram of cross-section of heart shows labels for SA node; internodal pathways; flow of cardiac impulse AV node; bundle of his; right bundle branch; spread of conduction from SA node to left atrium through interatrial pathways; left bundle branch; posterior fascicle of left bundle branch; anterior fascicle of left bundle branch; and Purkinje fibers.
B) Electrocardiogram shows PQ representing PR interval, peak QRS as QRS interval, and Q to T labeled as QT interval.
Source: (From Harding MM et al: Lewis’s Medical-surgical nursing: assessment and management of clinical problems, ed 11, St Louis, 2020, Elsevier.)
The conduction system of the heart generates the impulses needed to initiate the electrical chain of events for a normal heartbeat. The autonomic nervous system influences the rate of impulse generation and the speed of transmission through the conductive pathway and the strength of atrial and ventricular contractions. Sympathetic and parasympathetic nerve fibers innervate all parts of the atria and ventricles and the sinoatrial (SA) and atrioventricular (AV) nodes. Sympathetic fibers increase the rate of impulse generation and speed of transmission. The parasympathetic fibers originating from the vagus nerve decrease the rate (McCance and Huether, 2019).
The conduction system originates with the SA node, the “pacemaker” of the heart. The SA node is in the right atrium next to the entrance of the superior vena cava. Impulses are initiated at the SA node at an intrinsic rate of 60 to 100 cardiac action potentials per minute in an adult at rest. The electrical impulses are transmitted through the atria along intraatrial and internodal pathways to the AV node. The AV node mediates impulses between the atria and the ventricles. It assists atrial emptying by delaying the impulse before transmitting it through the bundle of His and the ventricular Purkinje network. A normal sinus rhythm is necessary to ensure optimal perfusion of the tissues in the body (McCance and Huether, 2019).
An electrocardiogram (ECG) is a measurement of the electrical activity of the conduction system. An ECG monitors the regularity and path of the electrical impulse through the conduction system; however, it does not reflect the muscular work of the heart. The normal sequence on the ECG is called the normal sinus rhythm (NSR) (see Fig. 41.3) (Urden et al., 2020).
NSR implies that the impulse originates at the SA node and follows the normal sequence through the conduction system. The P wave (atrial depolarization) represents the electrical conduction through both atria. Atrial contraction follows the P wave. The PR interval represents the impulse travel time from the SA node through the AV node, through the bundle of His, and to the Purkinje fibers. The normal length for the PR interval is 0.12 to 0.2 seconds. An increase in the time greater than 0.2 seconds indicates a block in the impulse transmission through the AV node, whereas a decrease, less than 0.12 seconds, indicates the initiation of the electrical impulse from a source other than the SA node (Urden et al., 2020).
The QRS complex (ventricular depolarization) indicates that the electrical impulse traveled through the ventricles. Normal QRS duration is 0.06 to 0.1 seconds. An increase in QRS duration indicates a delay in conduction time through the ventricles. Ventricular contraction usually follows the QRS complex (Urden et al., 2020).
The QT interval represents the time needed for ventricular depolarization and repolarization. The normal QT interval is 0.12 to 0.42 seconds. This interval varies inversely with changes in heart rate. Changes in electrolyte values, such as hypocalcemia or hypomagnesemia, or therapy with medications (disopyramide, amiodarone, haloperidol, and azithromycin are examples) increase the QT interval. An increased QT interval increases the person’s risk for lethal dysrhythmias (Urden et al., 2020).
Factors affecting oxygenation
Four types of factors influence the adequacy of circulation, ventilation, perfusion, and transport of respiratory gases to the tissues: (1) physiological, (2) developmental, (3) lifestyle, and (4) environmental. The physiological factors are discussed here, and the others are discussed in the Nursing Knowledge Base section that follows.
Physiological factors.
Any condition affecting cardiopulmonary functioning directly affects the ability of the body to meet oxygen demands. Respiratory disorders include hyperventilation, hypoventilation, and hypoxia. Cardiac disorders include disturbances in conduction, impaired valvular function, myocardial hypoxia, cardiomyopathy conditions, and peripheral tissue hypoxia. Other physiological processes affecting a patient’s oxygenation include alterations affecting the oxygen-carrying capacity of blood (anemia), decreased inspired oxygen concentration, increases in the metabolic demand of the body (fever), and alterations affecting chest wall movement caused by musculoskeletal abnormalities or neuromuscular alterations (muscular dystrophy) (McCance and Huether, 2019; Urden et al., 2020).
Decreased oxygen-carrying capacity.
Hemoglobin carries the majority of oxygen to tissues. Anemia and inhalation of toxic substances decrease the oxygen-carrying capacity of blood by reducing the amount of available hemoglobin to transport oxygen. Anemia (e.g., a lower-than-normal hemoglobin level) is a result of decreased hemoglobin production, increased red blood cell destruction, and/or blood loss. Patients have fatigue, decreased activity tolerance, increased breathlessness, increased heart rate, and pallor (especially seen in the conjunctiva of the eye). Oxygenation decreases as a secondary effect with anemia. The physiological response to chronic hypoxemia is the development of increased red blood cells (polycythemia). This is the adaptive response of the body to increase the amount of hemoglobin and the available oxygen-binding sites (Harding et al., 2020; McCance and Huether, 2019).
Carbon monoxide (CO) is a colorless, odorless gas that causes decreased oxygen-carrying capacity of blood. In CO toxicity, hemoglobin strongly binds with CO, creating a functional anemia. Because of the strength of the bond, CO does not easily dissociate from hemoglobin, making hemoglobin unavailable for oxygen transport. People with CO poisoning are often unaware of their exposure to this gas, and the symptoms of CO poisoning (headache, dizziness, nausea, vomiting, and dyspnea) mimic other illnesses (Urden et al., 2020).
Hypovolemia.
Conditions such as shock and severe dehydration cause extracellular fluid loss and reduced circulating blood volume, or hypovolemia. Decreased circulating blood volume results in hypoxia to body tissues. With significant fluid loss, the body tries to adapt by peripheral vasoconstriction and by increasing the heart rate to increase the volume of blood returned to the heart, thus increasing the cardiac output (McCance and Huether, 2019).
Decreased inspired oxygen concentration.
With the decline of the concentration of inspired oxygen, the oxygen-carrying capacity of the blood decreases. Decreases in the fraction of inspired oxygen concentration (FiO2) are caused by upper or lower airway obstruction, which limits delivery of inspired oxygen to alveoli; decreased environmental oxygen (at high altitudes); or hypoventilation (occurs in opiate overdoses) (Harding et al., 2020).
Increased metabolic rate.
Increased metabolic activity increases oxygen demand. An increased metabolic rate is normal in pregnancy, wound healing, and exercise because the body is using energy for building tissue. Most people are able to meet the increased oxygen demand and do not display signs of oxygen deprivation. The level of oxygenation declines when cardiopulmonary systems are unable to meet this demand.
For example, fever increases the tissues’ need for oxygen; as a result, carbon dioxide production increases. When fever persists, the metabolic rate remains high, and the body begins to break down protein stores. This causes muscle wasting and decreased muscle mass, including respiratory muscles such as the diaphragm and intercostal muscles. The body attempts to adapt to the increased carbon dioxide levels by increasing the rate and depth of respiration. The patient’s WOB increases, and the patient eventually displays signs and symptoms of hypoxemia. Patients with pulmonary diseases are at greater risk for hypoxemia (McCance and Huether, 2019).
Conditions affecting chest wall movement.
Any condition reducing chest wall movement results in decreased ventilation. If the diaphragm does not fully descend with breathing, the volume of inspired air decreases, delivering less oxygen to the alveoli and tissues (McCance and Huether, 2019).
Pregnancy.
As the fetus grows during pregnancy, the enlarging uterus pushes abdominal contents upward against the diaphragm. In the last trimester of pregnancy, the inspiratory capacity declines, resulting in dyspnea on exertion and increased fatigue (Ball et al., 2019).
Obesity.
Patients who are morbidly obese have reduced lung volumes from the heavy lower thorax and abdomen, particularly when in the recumbent and supine positions; this often causes obstructive sleep apnea. Morbid obesity creates a reduction in a patient’s lung and chest wall compliance as a result of encroachment of the abdomen into the chest, increased WOB, and decreased lung volumes. In some patients, an obesity-hypoventilation syndrome develops in which oxygenation is decreased and carbon dioxide is retained. The patient is also susceptible to atelectasis or pneumonia after surgery because the lungs do not expand fully and the lower lobes retain pulmonary secretions (McCance and Huether, 2019).
Musculoskeletal abnormalities.
Musculoskeletal impairments in the thoracic region reduce oxygenation. Such impairments result from abnormal structural configurations, trauma, muscular diseases, and diseases of the central nervous system. Abnormal structural configurations impairing oxygenation include those affecting the rib cage, such as pectus excavatum, and the vertebral column, such as kyphosis, lordosis, or scoliosis (Ball et al., 2019; McCance and Huether, 2019).
Trauma.
Any rib fracture or bruising causes pain and resultant reduced ventilation. Flail chest is a condition in which multiple rib fractures cause chest wall instability. This instability causes the lung under the injured area to contract on inspiration and bulge on expiration, resulting in hypoxia. Patients with thoracic or upper abdominal surgical incisions use shallow respirations to avoid pain, which decreases chest wall movement. Opioids for pain depress the respiratory center, further decreasing respiratory rate and chest wall expansion (Urden et al., 2020).
Neuromuscular diseases.
Neuromuscular diseases affect tissue oxygenation by decreasing a patient’s ability to expand and contract the chest wall. Ventilation is impaired, resulting in atelectasis, hypercapnia, and hypoxemia. Examples of conditions causing hypoventilation include myasthenia gravis and Guillain-Barré syndrome (McCance and Huether, 2019).
Central nervous system alterations.
Diseases or trauma of the medulla oblongata and/or spinal cord result in impaired ventilation. When the medulla oblongata is affected, neural regulation of ventilation is impaired, and abnormal breathing patterns develop. Cervical trauma at C3 to C5 usually results in paralysis of the phrenic nerve. When the phrenic nerve is damaged, the diaphragm does not descend properly, thus reducing inspiratory lung volumes and causing hypoxemia. Spinal cord trauma below the C5 vertebra usually leaves the phrenic nerve intact but damages nerves that innervate the intercostal muscles, preventing anteroposterior chest expansion.
Influences of chronic lung disease.
Oxygenation decreases as a direct consequence of chronic lung disease due to alveolar and/or airway alterations. Changes in the anteroposterior diameter of the chest wall (barrel chest) occur because of overuse of accessory muscles and air trapping in COPD or cystic fibrosis. Chronic lung disease results in varying degrees of dyspnea, tachypnea, hypoxemia, and/or hypercapnia (Ball et al., 2019; Harding et al., 2020; McCance and Huether, 2019).
Alterations in respiratory functioning
Illnesses and conditions affecting ventilation or oxygen transport alter respiratory functioning. The three primary alterations are hypoventilation, hyperventilation, and hypoxia.
The goal of ventilation is to produce a normal arterial carbon dioxide tension (PaCO2) between 35 and 45 mm Hg and a normal arterial oxygen tension (PaO2) between 80 and 100 mm Hg. Hypoventilation and hyperventilation are often determined by arterial blood gas analysis (McCance and Huether, 2019). Hypoxemia refers to a decrease in the amount of arterial oxygen. Nurses monitor arterial oxygen saturation (SpO2) using a pulse oximeter, a noninvasive oxygen saturation monitor. Normally SpO2 is greater than or equal to 95% (see Chapter 30).
Hypoventilation.
Hypoventilation occurs when alveolar ventilation is inadequate to meet the oxygen demand of the body or to eliminate sufficient carbon dioxide. As alveolar ventilation decreases, the body retains carbon dioxide. For example, atelectasis, a collapse of the alveoli, prevents normal exchange of oxygen and carbon dioxide. As more alveoli collapse, less of the lung is ventilated, and hypoventilation occurs.
In patients with COPD, the administration of excessive oxygen can result in hypoventilation. These patients have adapted to a high carbon dioxide level, so their carbon dioxide–sensitive chemoreceptors do not function normally. Their peripheral chemoreceptors of the aortic arch and carotid bodies are primarily sensitive to lower oxygen levels, causing increased ventilation. Because the stimulus to breathe is a decreased arterial oxygen (PaO2) level (hypoxic drive to breathe), administration of oxygen greater than 24% to 28% (1 to 3 L/min) prevents the PaO2 from falling to a level (60 mm Hg) that stimulates the peripheral receptors, thus destroying the stimulus to breathe. The resulting hypoventilation causes excessive retention of carbon dioxide, which can lead to respiratory acidosis and respiratory arrest. Signs and symptoms of hypoventilation include mental status changes, dysrhythmias, and potential cardiac arrest. If untreated, the patient’s status rapidly declines, leading to convulsions, unconsciousness, and death (McCance and Huether, 2019).
Hyperventilation.
Hyperventilation is a state of ventilation in which the lungs remove carbon dioxide faster than it is produced by cellular metabolism. Severe anxiety, infection, drugs, or an acid-base imbalance induces hyperventilation (see Chapter 42). Acute anxiety leads to hyperventilation and exhalation of excessive amounts of carbon dioxide. Increased body temperature (fever) increases the metabolic rate, thereby increasing carbon dioxide production. The increased carbon dioxide level stimulates an increase in the patient’s rate and depth of respiration, causing hyperventilation (McCance and Huether, 2019).
Hyperventilation is sometimes chemically induced. For example, salicylate (aspirin) poisoning and amphetamine use result in excess carbon dioxide production, stimulating the respiratory center to compensate by increasing the rate and depth of respiration. It also occurs as the body tries to compensate for metabolic acidosis. For example, the patient with diabetes in ketoacidosis produces large amounts of metabolic acids. The respiratory system tries to correct the acid-base balance by overbreathing. Ventilation increases to reduce the amount of carbon dioxide available to form carbonic acid (see Chapter 42). This can also result in the patient developing respiratory alkalosis. Signs and symptoms of hyperventilation include rapid respirations, sighing breaths, numbness and tingling of hands/feet, light-headedness, and loss of consciousness (McCance and Huether, 2019).
Hypoxia.
Hypoxia is inadequate tissue oxygenation at the cellular level. It results from a deficiency in oxygen delivery or oxygen use at the cellular level. It is a life-threatening condition. Untreated, it has the potential to produce fatal cardiac dysrhythmias (McCance and Huether, 2019).
Causes of hypoxia include (1) a decreased hemoglobin level and lowered oxygen-carrying capacity of the blood; (2) a diminished concentration of inspired oxygen, which occurs at high altitudes; (3) the inability of the tissues to extract oxygen from the blood, as with cyanide poisoning; (4) decreased diffusion of oxygen from the alveoli to the blood, as in pneumonia or pulmonary edema; (5) poor tissue perfusion with oxygenated blood, as with shock; and (6) impaired ventilation, as with multiple rib fractures or chest trauma (McCance and Huether, 2019).
The clinical signs and symptoms of hypoxia include apprehension, restlessness (often an early sign), inability to concentrate, decreased level of consciousness, dizziness, and behavioral changes. The patient with hypoxia is unable to lie flat and appears both fatigued and agitated. Vital sign changes include an increased pulse rate and increased rate and depth of respiration. During early stages of hypoxia the blood pressure is elevated unless the condition is caused by shock. As the hypoxia worsens, the respiratory rate declines as a result of respiratory muscle fatigue (Harding et al., 2020).
Cyanosis, blue discoloration of the skin and mucous membranes caused by the presence of desaturated hemoglobin in capillaries, is a late sign of hypoxia. The presence or absence of cyanosis is not a reliable measure of oxygen status. Central cyanosis, observed in the tongue, soft palate, and conjunctiva of the eye where blood flow is high, indicates hypoxemia. Peripheral cyanosis, seen in the extremities, nail beds, and earlobes, is often a result of vasoconstriction and stagnant blood flow (Ball et al., 2019; Harding et al., 2020).
Alterations in cardiac functioning
Illnesses and conditions affecting cardiac rhythm, strength of contraction, blood flow through the heart or to the heart muscle, and decreased peripheral circulation alter cardiac function. For example, older adults have structural changes in the heart, including vascular and valve stiffening, increased left ventricular wall thickness, and changes in the conduction system. Chronic heart disease, including heart failure and coronary artery disease, is the number one chronic disease in the United States (CDC, 2021f).
Disturbances in conduction.
Electrical impulses that do not originate from the SA node cause conduction disturbances. These rhythm disturbances are called dysrhythmias, meaning a deviation from the normal sinus heart rhythm. Dysrhythmias occur as a primary conduction disturbance such as in response to ischemia; valvular abnormality; anxiety; drug toxicity; caffeine, alcohol, or tobacco use; or a complication of acid-base or electrolyte imbalance (see Chapter 42).
Dysrhythmias are classified by cardiac response and site of impulse origin. Cardiac response is tachycardia (greater than 100 beats/min), bradycardia (less than 60 beats/min), a premature (early) beat, or a blocked (delayed or absent) beat. Tachydysrhythmias and bradydysrhythmias lower cardiac output and blood pressure. Tachydysrhythmias reduce cardiac output by decreasing diastolic filling time. Bradydysrhythmias lower cardiac output because of the decreased heart rate (McCance and Huether, 2019; Urden et al., 2020).
Atrial fibrillation is a common dysrhythmia in older adults. The electrical impulse in the atria is chaotic and originates from multiple sites. The rhythm is irregular because of the multiple pacemaker sites and the unpredictable conduction to the ventricles. The QRS complex is normal; however, it occurs at irregular intervals. Atrial fibrillation is often described as an irregularly irregular rhythm. It decreases cardiac output by altering preload and contractility (Hartjes, 2018; McCance and Huether, 2019; Urden et al., 2020).
Abnormal impulses originating above the ventricles are supraventricular dysrhythmias. The abnormality on the waveform is the configuration and placement of the P wave. Ventricular conduction usually remains normal, and there is a normal QRS complex. Paroxysmal supraventricular tachycardia is a sudden, rapid onset of tachycardia originating above the AV node. It often begins and ends spontaneously. Sometimes excitement, fatigue, caffeine, smoking, or alcohol use precipitates paroxysmal supraventricular tachycardia (McCance and Huether, 2019; Urden et al., 2020).
Ventricular dysrhythmias represent an ectopic site of impulse formation within the ventricles. They are ectopic in that the impulse originates in the ventricle, not the SA node. The configuration of the QRS complex is usually widened and bizarre. P waves are not always present; often they are buried in the QRS complex. Ventricular tachycardia and ventricular fibrillation are life-threatening rhythms that require immediate intervention. Ventricular tachycardia is a life-threatening dysrhythmia because of the decreased cardiac output and the potential to deteriorate into ventricular fibrillation or sudden cardiac death (Hartjes, 2018; Urden et al., 2020).
Altered cardiac output.
Failure of the myocardium to eject sufficient volume to the systemic and pulmonary circulations occurs in heart failure. Primary coronary artery disease, cardiomyopathy, valvular disorders, and pulmonary disease lead to myocardial pump failure (McCance and Huether, 2019; Urden et al., 2020).
Left-sided heart failure.
Left-sided heart failure is an abnormal condition characterized by decreased functioning of the left ventricle. If left ventricular failure is significant, the amount of blood ejected from the left ventricle drops greatly, resulting in decreased cardiac output. Signs and symptoms include fatigue, breathlessness, dizziness, and confusion as a result of tissue hypoxia from the diminished cardiac output. As the left ventricle continues to fail, blood begins to pool in the pulmonary circulation, causing pulmonary congestion. Clinical findings include crackles in the bases of the lungs on auscultation, hypoxia, shortness of breath on exertion, cough, and paroxysmal nocturnal dyspnea (Hartjes, 2018; McCance and Huether, 2019).
Right-sided heart failure.
Right-sided heart failure results from impaired functioning of the right ventricle. It more commonly results from pulmonary disease or as a result of long-term left-sided failure. The primary pathological factor in right-sided failure is elevated pulmonary vascular resistance (PVR). As the PVR continues to rise, the right ventricle works harder, and the oxygen demand of the heart increases. As the failure continues, the amount of blood ejected from the right ventricle declines, and blood begins to “back up” in the systemic circulation. Clinically the patient has systemic symptoms, such as weight gain, distended neck veins, hepatomegaly and splenomegaly, and dependent peripheral edema (Hartjes, 2018; McCance and Huether, 2019).
Impaired valvular function.
Valvular heart disease is an acquired or congenital disorder of a cardiac valve that causes either hardening (stenosis) or impaired closure (regurgitation) of the valves. When stenosis occurs, the flow of blood through the valves is obstructed. For example, when stenosis occurs in the semilunar valves (aortic and pulmonic valves), the adjacent ventricles have to work harder to move the ventricular blood volume beyond the stenotic valve. Over time the stenosis causes the ventricle to hypertrophy (enlarge), and if the condition is untreated, left- or right-sided heart failure occurs. When regurgitation occurs, there is a backflow of blood into an adjacent chamber. For example, in mitral regurgitation the mitral leaflets do not close completely. When the ventricles contract, blood escapes back into the atria, causing a murmur, or “whooshing” sound (see Chapter 30) (Hartjes, 2018; McCance and Huether, 2019).
Myocardial ischemia.
Myocardial ischemia results when the supply of blood to the myocardium from the coronary arteries is insufficient to meet myocardial oxygen demands. Two common outcomes of this ischemia are angina pectoris and myocardial infarction (Hartjes, 2018; McCance and Huether, 2019).
Angina.
Angina pectoris is a transient imbalance between myocardial oxygen supply and demand. The condition results in chest pain that is aching, sharp, tingling, or burning or that feels like pressure. Typically, chest pain is left sided or substernal and often radiates to the left or both arms, the jaw, neck, and back. In some patients, angina pain does not radiate. It usually lasts from 3 to 5 minutes. Patients report that it is often precipitated by activities that increase myocardial oxygen demand (e.g., eating heavy meals, exercise, or stress). It is usually relieved with rest and coronary vasodilators, the most common being a nitroglycerin preparation.
Women have different symptoms or no symptoms at all. Some will also have atypical symptoms, such as palpitations, anxiety, weakness, and fatigue. In addition, many women with angina will have ischemia noted on electrocardiogram, but no evidence of coronary artery disease (McCance and Huether, 2019).
Myocardial infarction.
Myocardial infarction (MI) or acute coronary syndrome (ACS) results from sudden decreases in coronary blood flow or an increase in myocardial oxygen demand without adequate coronary perfusion. Infarction occurs because ischemia is not reversed. Cellular death occurs after 20 minutes of myocardial ischemia (McCance and Huether, 2019).
Chest pain associated with MI in men is usually described as crushing, squeezing, or stabbing. The pain is often in the left chest and sternal area; may be felt in the back; and radiates down the left arm to the neck, jaws, teeth, epigastric area, and back. It occurs at rest or exertion and lasts more than 20 minutes. Rest, position change, or sublingual nitroglycerin administration does not relieve the pain (Hartjes, 2018; McCance and Huether, 2019).
There are differences between men and women in relation to coronary artery disease. As women get older, their risk of heart disease begins to rise, making it the leading cause of death for women in the United States. Women on average have greater blood cholesterol and triglyceride levels than men. Obesity in women is more prevalent, which also increases risk for diabetes and cardiac disease. Women’s symptoms differ from those of men. The most common initial symptom in women is angina, but they also present with atypical symptoms such as fatigue, indigestion, shortness of breath, and back or jaw pain. Women have twice the risk of dying within the first year after a heart attack than men (CDC, 2020a; Ball et al., 2019; Harding et al., 2020).
Nursing knowledge base
Factors influencing oxygenation
In addition to physiological factors, multiple developmental, lifestyle, and environmental factors affect patients’ oxygenation status. It is important to recognize these as possible risks or factors that impact their health care goals.
Developmental factors.
The developmental stage of a patient and the normal aging process affect tissue oxygenation.
Infants and toddlers.
Healthy full-term infants younger than 3 months of age are presumed to have a lower infection rate because of the protective function of maternal antibodies. The infection rate increases in infants from 3 to 6 months of age. Infants and toddlers are at risk for upper respiratory tract infections, especially when they are exposed to secondhand smoke or other children. Upper respiratory tract infections are usually not dangerous, and infants and toddlers recover with little difficulty. Infants and toddlers are also at risk for airway obstruction because of their anatomically smaller airways and their tendency to place foreign objects in their mouths (Hockenberry et al., 2019).
School-age children and adolescents.
School-age children and adolescents are exposed to respiratory infections and respiratory risk factors such as cigarette smoking or secondhand smoke. This age-group is also at risk for experimenting with cigarette smoking and other recreational inhalants. A healthy child usually does not have adverse pulmonary effects from respiratory infections. The CDC (2018a) reported that 5.6% of middle school–age children and 19.6% of high school–age children use tobacco products, with electronic cigarettes being the most commonly used tobacco product among these age-groups. School-age children and adolescents possess other cardiopulmonary disease risk factors such as obesity, inactive lifestyles, unhealthy diets, and excessive use of caffeinated beverages or other energy drinks (Hockenberry et al., 2019).
Young and middle-age adults.
Young and middle-age adults are exposed to multiple cardiopulmonary risk factors: an unhealthy diet, lack of exercise, stress, over-the-counter and prescription drugs not used as intended, illegal substances, and smoking. Reducing these modifiable factors decreases a patient’s risk for cardiac or pulmonary diseases. This is also the time when individuals establish lifelong habits and lifestyles. It is important to help your patients make good choices and informed decisions about their health care practices. The increased cost of cigarettes plus the states’ smoke-free air policies, laws that reduce smoking in public places, and access to cessation programs and medications have proven to be helpful in smoking cessation (CDC, 2018b).
Older adults.
The cardiac and respiratory systems undergo changes throughout the aging process (Box 41.1). The changes are associated with calcification of the heart valves, vascular stiffening and increased left ventricular wall thickness, impaired SA node function, and costal cartilage stiffening. The arterial system develops atherosclerotic plaques.
BOX 41.1
FOCUS ON OLDER ADULTS
Cardiopulmonary Implication in Older Adults
• Older patients are at an increased risk for developing tuberculosis (TB) through exposure or reactivation of dormant organisms that were present for decades (CDC, 2019).
• When screening older adults for TB, a two-step process is used. The standard 5-TU Mantoux test is given and repeated or repeated with the 250-TU strength to create a booster effect. If the older patient has a positive reaction, a complete history is necessary to determine any risk factors.
• Cardiac problems differ from other chronic conditions in that when they become acute, symptoms worsen rapidly and necessitate hospitalization, whereas other chronic conditions can be managed in the home (Touhy and Jett, 2018).
• Controlling blood pressure in older adults results in 30% fewer strokes, 64% less heart failure, 23% fewer fatal cardiac events, and 21% fewer cardiac-related deaths (Touhy and Jett, 2018).
• Mental status changes are often the first signs of cardiac and/or respiratory problems and often include forgetfulness and irritability.
• Changes in the older adult’s cough mechanism lead to retention of pulmonary secretions, airway occlusion, and atelectasis if patients do not use cough suppressants with caution.
• Age-related changes in the immune system lead to a decline of both cell-mediated and humoral immunity, resulting in an increased risk of respiratory infections (McCance and Huether, 2019).
• Changes in the thorax that occur from ossification of costal cartilage, decreased space between vertebrae, and diminished respiratory muscle strength lead to problems with chest expansion and oxygenation (Touhy and Jett, 2018).
Osteoporosis leads to changes in the size and shape of the thorax. The trachea and large bronchi become enlarged from calcification of the airways. The alveoli enlarge, decreasing the surface area available for gas exchange. The number of functional cilia is reduced, causing a decrease in the effectiveness of the cough mechanism, putting the older adult at increased risk for respiratory infections (Touhy and Jett, 2018).
Lifestyle factors.
Lifestyle modifications are difficult for patients because they often have to change an enjoyable habit, such as smoking cigarettes or eating certain foods. Risk-factor modification is important and includes smoking cessation, weight reduction, a low-cholesterol and low-sodium diet, management of hypertension, and moderate exercise (see Chapter 6). Although it is difficult to change long-term behavior, helping patients acquire healthy behaviors reduces the risk for or slows or halts the progression of cardiopulmonary diseases.
Nutrition.
Good nutrition affects cardiopulmonary function by supporting normal metabolic functions. A poor diet leads to risk factors affecting the heart and lungs. Without essential nutrients, a patient may experience respiratory muscle wasting, resulting in decreased muscle strength and respiratory excursion. Cough efficiency is reduced secondary to respiratory muscle weakness, putting a patient at risk for retention of pulmonary secretions. A patient with chronic lung disease often requires a diet higher in calories and smaller, more frequent meals due to the increased work of breathing. A diet with a moderate amount of carbohydrates is recommended to prevent an increase in carbon dioxide production. Obesity affects the respiratory and cardiovascular systems. It can lead to a decrease in lung expansion and an increase in oxygen demand to meet metabolic demands (Harding et al., 2020).
Dietary practices also influence the prevalence of cardiovascular diseases (see Chapter 45). Patients with nutritional alterations are at risk for anemia, which reduces the oxygen-carrying capacity of the blood and can alter cardiac output. Cardioprotective nutrition includes diets rich in fiber; whole grains; fresh fruits and vegetables; nuts; antioxidants; lean meats, fish, and chicken; and omega-3 fatty acids. A diet of fruits, vegetables, and low-fat dairy foods that are high in fiber, potassium, calcium, and magnesium and low in saturated and total fat helps prevent and reduce the effects of hypertension (Harding et al., 2020).
Hydration.
Fluid intake is essential for cellular health. Fluid volume overload may lead to vascular congestion in patients with heart, kidney, or lung diseases and impair the body’s ability to deliver oxygen to the tissues. Dehydration or fluid volume deficit may result in dizziness, fainting, hypotension, or a thickening of respiratory secretions, which makes it difficult for a patient to expectorate secretions (Harding et al., 2020).
Exercise.
Exercise increases the metabolic activity and oxygen demand of the body. The rate and depth of respiration increase, enabling the person to inhale more oxygen and exhale excess carbon dioxide. A physical exercise program has many benefits (see Chapter 38). People who exercise for 30 to 60 minutes daily have a lower pulse rate and blood pressure, decreased cholesterol level, increased blood flow, and greater oxygen extraction by working muscles (Harding et al., 2020).
Smoking.
Cigarette smoking and secondhand smoke are associated with a number of diseases, including heart disease, COPD, and lung cancer. Cigarette smoking worsens peripheral vascular and coronary artery diseases. Inhaled nicotine causes vasoconstriction of peripheral and coronary blood vessels, increasing blood pressure and decreasing blood flow to peripheral vessels (McCance and Huether, 2019).
Women who take birth control pills and smoke cigarettes have an increased risk for thrombophlebitis and pulmonary emboli. Smoking during pregnancy can result in low-birth-weight babies, preterm delivery, and babies with reduced lung function (CDC, 2020a).
Smoking accounts for approximately 30% of all cancer deaths in the United States, including 80% of all lung cancer deaths. Smoking has been linked to the development of other cancers, including cancers of the mouth, esophagus, liver, bladder, kidney, and cervix, and myeloid leukemia (ACS, 2020a). Nicotine patches, gum, and lozenges are available over the counter, and nicotine nasal spray and inhalers can be obtained by prescription. Prescription drugs such as bupropion and varenicline are also available to help people quit smoking (ACS, 2020b).
Exposure to environmental tobacco smoke (secondhand smoke) increases the risk of lung cancer and cardiovascular disease in the nonsmoker. Children with parents who smoke have a higher incidence of asthma, pneumonia, and ear infections. Infants exposed to secondhand smoke are at higher risk for sudden infant death syndrome (NCI, 2018).
Substance abuse.
Excessive use of alcohol and other illicit drugs impairs tissue oxygenation in two ways. First, the person who chronically abuses substances often has a poor nutritional intake. With the resultant decrease in intake of iron-rich foods, hemoglobin production declines. Second, excessive use of alcohol and certain other drugs depresses the respiratory center, reducing the rate and depth of respiration and the amount of inhaled oxygen. Substance abuse by either smoking or inhaling substances such as crack cocaine or fumes from paint or glue cans causes direct injury to lung tissue that leads to permanent lung damage (McCance and Huether, 2019). The report on inhalant abuse (huffing) by teenagers to get a euphoric effect includes use of a wide variety of substances such as paint thinner, nail polish remover, glue, spray paint, nitrous oxide, and other common household products. Sudden death can occur from cardiac arrhythmias, or chronic abuse can cause damage to heart, lungs, and kidneys (NIDA, 2020).
Stress.
Stress is a perceived threat that results in sympathetic stimulation. Continuous stress adversely affects a patient’s health and well-being (see Chapter 37). A continuous state of stress increases the metabolic rate and oxygen demand of the body. The body responds to stress with an increased rate and depth of respiration and increased cardiac output. Stress causes an increased release of cortisol, which affects the metabolism of fat and creates a risk for CAD and hypertension. Stressors can be a trigger for asthma exacerbations. Patients with chronic illnesses or life-threatening illnesses cannot tolerate the oxygen demands associated with stress (McCance and Huether 2019).
Environmental factors.
Consider a patient’s environment. Rural populations have more COPD-related issues that are not directly related to the environment but rather related to more people smoking, increased exposure to secondhand smoke, less access to smoking cessation programs, and a higher likelihood of rural residents being uninsured (CDC, 2018c). A patient’s workplace sometimes increases the risk for pulmonary disease. Occupational pollutants include asbestos, talcum powder, dust, and airborne fibers. For example, farm workers in dry regions of the southwestern United States are at risk for coccidioidomycosis, a fungal disease caused by inhalation of spores of the airborne bacterium Coccidioides immitis (CDC, 2020b). Asbestosis is an occupational lung disease that develops after exposure to asbestos. The lung with asbestosis often has diffuse interstitial fibrosis, creating a restrictive lung disease. Patients exposed to asbestos are at risk for developing lung cancer, and this risk increases with exposure to tobacco smoke (McCance and Huether, 2019).
John uses his knowledge of the pulmonary system and the impact of certain risk factors on pulmonary functioning to plan a complete cardiopulmonary assessment for Mr. Edwards. John’s prior experience in health assessment and his clinical judgment help him to target important assessment areas without increasing Mr. Edwards’ respiratory distress or worsening his fatigue. Before he begins the assessment, he reviews Mr. Edwards’ medical record and notes that Mrs. Edwards has a smoking history.
Critical thinking
Caring for patients with impaired oxygenation can be complex. Clinical judgment in applying the nursing process requires critical thinking, the synthesis of knowledge, experience, environmental factors, data gathered from patients, critical thinking attitudes, and intellectual and professional standards to ensure safe and appropriate care. Clinical judgments and critical thinking require you to anticipate information, analyze the data, recognize cues, and make decisions about your patient’s care. During assessment consider all elements that will assist you to make clinical decisions for identifying appropriate nursing diagnoses (Fig. 41.4).
FIG. 41.4Critical thinking model for oxygenation assessment.
Components of critical thinking leading to nursing process demonstrated through an oval illustration that shows three concentric levels. The components of critical thinking are as follows:
• Knowledge Base: Cardiopulmonary anatomy and physiology, cardiopulmonary pathophysiology, physiological factors affecting oxygenation, pharmacological factors affecting oxygenation, environmental factors affecting oxygenation, developmental factors affecting oxygenation, risk factors for impaired oxygenation, signs and symptoms of impaired oxygenation, and effects of patient’s illness or disability on patient’s oxygenation and energy needs.
• Environment: The presence of medical devices that may impact time and complexity when providing care, available resources or equipment to improve patient’s oxygenation, and need for additional necessary personnel interventions.
• Experience: Experience caring for patients with cardiopulmonary conditions, experience observing patient responses to oxygen therapies, personal experiences with cardiopulmonary alterations (for example respiratory infections, heart disease).
• Standards: ANA standards and scope of nursing practice, clinical practice guidelines and standards of practice, intellectual standards in measurement, agency policies and procedures, and professional includes standards of care (for example American cancer society, American heart association, American association for respiratory care) and ethical standards.
• Attitudes: Display confidence when assessing extent of patient’s cardiopulmonary alterations and use creativity when assessing cultural factors influencing patient’s risk factors and care needs.
The three concentric levels, marked inside to outside as follows:
• Clinical decision making.
• Recognize cues and analyze cues (interconnected), prioritize hypotheses and generate solutions (interconnected), and take actions and evaluate outcomes (interconnected).
• Assessment, analysis or diagnosis, planning, implementation, and evaluation.
Source: (Clinical Judgment Measurement Model copyright © NCSBN. All rights reserved.)
Knowledge of cardiac and respiratory physiology and oxygen supply and demand provides a scientific basis for how you approach an assessment for your patient. As you conduct your assessment, also consider the pathogenesis and impact on the overall health and function in a patient with cardiopulmonary diseases and the potential effects of underlying diseases. Critical thinking attitudes ensure that you approach patient care in a methodical and logical way. For example, you will assess a patient who has coronary artery disease, chronic lung disease, and diabetes differently from a patient who has pneumonia and diabetes. Assessment will differ by the nature of a patient’s condition. A patient with primary heart problems will have a cardiac focus, whereas a condition such as pneumonia has a pulmonary focus. Use clinical judgment to integrate what you learn about your patient, knowledge from nursing and other disciplines, past experience with other patients, and relevant clinical guidelines. The use of professional standards such as those of the American Association for Respiratory Care (AARC) and the American Nurses Association (ANA) provides valuable guidance in the care and management of patients (see Fig. 41.4). Your ability to manage the care of patients with alterations in oxygenation will improve as you gain experience and competency.
Nursing process
Apply clinical judgment as you use the nursing process and a critical thinking approach in your care of patients. The nursing process provides a clinical decision-making approach for you to develop and implement a patient-centered, individualized plan of care.
Assessment
During the assessment process, thoroughly assess each patient, critically analyze findings, and identify cues to ensure that you make patient-centered clinical decisions about the nature of a patient’s health problems. You will use clinical judgment by assessing a patient’s presenting condition and comparing with signs and symptoms anticipated from known medical conditions to identify if physical manifestations of altered oxygenation exist. Nursing assessment includes an in-depth history of a patient’s normal and present cardiopulmonary function; past impairments in cardiac, circulatory, or respiratory functioning; and methods that a patient uses to optimize oxygenation. The nursing history includes a review of drug, food, and other allergies. Physical examination of a patient’s cardiopulmonary status reveals the extent of existing signs and symptoms (Ball et al., 2019) (see Chapter 30). Utilizing assessment values of pulse oximetry and capnography aids in the assessment of patients with spontaneous breathing, patients who are intubated, and patients requiring oxygen therapy or mechanical ventilation. Pulse oximetry provides instant feedback about the patient’s level of oxygenation. Capnography, also known as end-tidal CO2 monitoring, provides instant information about the patient’s ventilation (how effectively CO2 is being eliminated by the pulmonary system), perfusion (how effectively CO2 is being transported through the vascular system), and how effectively CO2 is produced by cellular metabolism (Hartjes, 2018; Urden et al., 2020). Capnography is measured near the end of exhalation. Finally, a review of laboratory and diagnostic test results provides valuable assessment data.
Through the patient’s eyes.
As you conduct your assessments, ask patients about their priorities and what they expect from their health care visit. Identifying their expectations regarding their health, symptoms, and treatment plan ensures you involve patients in the decision-making process, which helps them participate in their care. For example, planning an exercise program for a patient who expresses a desire to improve activity tolerance helps meet the patient’s health objectives. In contrast, planning a smoking-cessation program for a patient who is not ready for the change is frustrating for both the patient and you.
Establish realistic short-term outcomes. For example, exercise programs and tobacco-cessation treatments are effective in improving cardiopulmonary functioning, but a patient needs to be willing to participate in the program and may need to use several short-term strategies to be successful. Educating the patient on the opportunities for individual, group, or telephone counseling and identifying a social support system give more individual choices when developing the plan. Various community centers have several exercise programs individualized to a person’s specific outcomes. When smoking cessation is a patient priority, there are smoking-cessation programs and various nicotine and non-nicotine medications that can be discussed to identify one that fits the patient’s lifestyle. A combination of counseling and medication is more effective than either one alone (CDC, 2018b).
Remember that your outcomes and expectations do not always coincide with those of your patient. By addressing a patient’s concerns and expectations, you establish a relationship that addresses how to achieve expected outcomes. Knowing your patients’ perspectives and expectations and respecting their wishes go a long way in helping them make significant beneficial lifestyle changes.
Nursing history.
The nursing history focuses on the patient’s ability to meet oxygen needs and maintain cardiopulmonary health. The nursing history for respiratory function includes ruling out the presence of a cough, shortness of breath, dyspnea, wheezing, pain, environmental exposures, frequency of respiratory tract infections, pulmonary risk factors, past respiratory problems, current medication use, and smoking history or secondhand smoke exposure. The nursing history for cardiac function includes pain and characteristics of pain, fatigue, peripheral circulation, cardiac risk factors, diet, and the presence of past or concurrent cardiac conditions. Assessment data are often similar for respiratory and cardiac health problems. Thus it is important to ask specific questions related to cardiopulmonary disease and to carefully analyze all assessment findings for cues that indicate potential reasons and treatments for a patient’s altered oxygenation (Box 41.2).
BOX 41.2
Nursing Assessment Questions
Nature of the cardiopulmonary problem
• Describe the problem that you’re having with your heart.
• Does the problem (e.g., chest pain, rapid heart rate) occur at a specific time of the day, during or after exercise, or all the time?
• Do you notice abnormal beats? Do these occur at a specific time of day or during/after activity? What makes these abnormal beats better or worse?
• Does your problem affect your ability to perform daily activity?
Questions to ask associated with breathing
• Describe the breathing problems you are having.
• How has your breathing pattern changed?
• Do you have a cough? Is the coughing increasing? Is it worse at a certain time of day?
• Describe your cough. Is it dry or moist? Do you have sputum with coughing? Is this different in color, volume, or thickness?
• On a scale of 0 to 10, with 10 being the most severe, rate your shortness of breath. What helps your shortness of breath?
Questions to ask related to chest pain
• If you are having chest pain, what causes the pain and how long does it last? Is this a different type of pain? What relieves or worsens it? Show me where the pain is located.
• Does the chest pain occur with coughing?
• On a scale of 0 to 10, with 0 being no pain and 10 being the most severe pain, rate your chest pain at its worst. How would you describe your pain? Is the pain different today?
• Do you have any other symptoms, such as nausea, numbness and tingling in your arm, palpitations, or anxiety, when you have chest pain?
Questions to ask regarding predisposing factors
• Have you been exposed to a cold or flu or other respiratory illnesses?
• Tell me the medications you are taking. Are you taking over-the-counter medications or supplements? If so, what are they?
• Do you smoke? How long have you smoked? How much do you smoke during a day? Have you been exposed to secondhand smoke?
• Have you been doing any unusual exercises?
Questions to ask regarding effect of symptoms
• Describe for me a typical daily diet.
• Tell me how your symptoms affect your daily activities, appetite, sleeping, and exercise routine.
Health risks.
Determine familial risk factors such as a family history of lung cancer or cardiovascular disease. Documentation includes blood relatives who had cardiopulmonary disease and their present level of health or age at time of death. Assess for an exposure to infectious organisms, such as tuberculosis (TB). Also assess for occupational and environmental risk factors (e.g., asbestos exposure) (Ball et al., 2019; McCance and Huether, 2019).
Pain.
The presence of chest pain requires an immediate thorough assessment, including location, duration, radiation, and frequency. In addition, it is important to note any other symptoms associated with chest pain, such as nausea, diaphoresis, extreme fatigue, or weakness. Cardiac pain does not occur with respiratory variations. Chest pain in men is most often on the left side of the chest and radiates to the left arm. Chest pain in women is much less definitive and often manifests itself as a sensation of breathlessness, jaw or back pain, nausea, and/or fatigue (CDC, 2020a). Pericardial pain results from inflammation of the pericardial sac, occurs on inspiration, and does not usually radiate (Ball et al., 2019).
Pleuritic chest pain results from inflammation of the pleural space of the lungs; the pain is peripheral and radiates to the scapular regions. Inspiratory maneuvers such as coughing, yawning, and sighing worsen pleuritic chest pain. Patients usually describe it as knifelike, lasting from a minute to hours and always in association with inspiration. Musculoskeletal pain is often present following exercise, rib trauma, and prolonged coughing episodes. Inspiration worsens this pain, and patients often confuse it with pleuritic chest pain (Ball et al., 2019).
Fatigue.
Fatigue is a subjective sensation in which a patient reports a loss of endurance. Fatigue in the patient with cardiopulmonary alterations is often an early sign of a worsening of the chronic underlying process. To provide an objective measure of fatigue, ask the patient to rate it on a scale of 0 to 10, with 10 being the worst level and 0 representing no fatigue. Ask your patients when they noticed the fatigue, what makes it better or worse, if the onset was sudden or gradual, if it is worse in the morning or later in the day, and how the fatigue affects what they want to do (Ball et al., 2019; Harding et al., 2020).
Dyspnea.
Dyspnea is associated with hypoxia. It is the subjective sensation of difficult or uncomfortable breathing or observed labored breathing with shortness of breath. Dyspnea is usually associated with exercise or excitement, but in some patients it is present without any relation to activity or exercise. It is associated with many conditions, such as pulmonary diseases, cardiovascular diseases, neuromuscular conditions, and anemia. In addition, it occurs in the pregnant woman in the final months of pregnancy. Finally, environmental factors such as pollution, cold air, and smoking also cause or worsen dyspnea (Ball et al., 2019).
When gathering information about a patient’s sensation of dyspnea, ask the patient when the dyspnea occurs (such as with exertion, stress, or respiratory tract infection) and what improves the dyspnea (e.g., rest, inhaled medication, or position change). Determine whether the patient’s dyspnea affects the ability to lie flat. Orthopnea is an abnormal condition in which a patient uses multiple pillows when reclining to breathe easier or sits leaning forward with arms elevated. The number of pillows used usually helps to quantify the orthopnea (e.g., two- or three-pillow orthopnea). Also ask whether the patient must sleep in a recliner chair to breathe easier. Paroxysmal nocturnal dyspnea (PND) occurs when a patient is sleeping. The patient often awakens in a panic, feels a sensation of suffocating, and has a strong need to sit up to relieve the breathlessness (Ball et al., 2019).
Cough.
Coughing is a protective reflex to clear the trachea, bronchi, and lungs of irritants and secretions. Patients with a chronic cough tend to deny, underestimate, or minimize their coughing, often because they are so accustomed to it that they are unaware of its frequency (Ball et al., 2019).
If a patient has a cough, determine the onset of the cough, how frequently it occurs, and whether it is productive or nonproductive. Chronic coughs are often a sign of chronic lung disease, whereas acute coughs can be a sign of infection or an inhaled irritant. A nonproductive cough is often associated with allergies or gastroesophageal reflux disease. A productive cough results in sputum production (e.g., material coughed up from the lungs that a patient swallows or expectorates). Sputum contains mucus, cellular debris, microorganisms, and sometimes pus or blood. Collect data about the type and quantity of sputum. Instruct patients to try to cough up some sputum and not to simply clear the throat, which produces only saliva. Have the patient cough into a specimen cup. Inspect the sputum for color (such as green or blood tinged), consistency (such as thin or thick), odor (none or foul), and amount in tablespoons or milliliters (Ball et al., 2019).
If hemoptysis (bloody sputum) is present, determine whether it is associated with coughing and bleeding from the upper respiratory tract, sinus drainage, or the gastrointestinal tract (hematemesis). Hemoptysis has an alkaline pH, and hematemesis has an acidic pH; thus, pH testing of the specimen may help to determine the source (McCance and Huether, 2019). Describe hemoptysis according to amount and color and whether it is mixed with sputum. Note whether the patient is on anticoagulant therapy. When there is bloody or blood-tinged sputum, health care providers frequently perform diagnostic tests such as examination of sputum specimens, chest x-ray examinations, bronchoscopy, and other scans.
Environmental and occupational factors.
Environmental exposure to inhaled substances, such as smog, dust, silicon, mold, cockroaches, pet dander, and asbestos, is linked with respiratory disease. Investigate exposures in the patient’s home, workplace, and recent travel. In addition, determine whether a patient who is a nonsmoker is exposed to secondhand smoke (ATSDR, 2018; McCance and Huether, 2019).
Carbon monoxide (CO) poisoning often results from an improperly vented furnace flue or fireplace. The patient will have vague complaints of general malaise, flulike symptoms, and excessive sleepiness. Patients are particularly at risk in the late fall when they turn the furnace on or begin to use the fireplace again (CDC, 2020c). Ask whether there is a CO detector in the home.
Radon gas is a radioactive substance from the breakdown of uranium in soil, rock, and water that enters homes through the ground or well water. When homes are poorly ventilated, this gas is unable to escape and becomes trapped. If a patient who smokes also lives in a home with a high radon level, the risk for lung cancer is very high (EPA, 2016). Ask whether the patient has any radon detectors in the home.
Smoking.
It is important to determine a patient’s direct and secondary exposure to tobacco. Ask about any history of smoking; include the number of years smoked and the number of packages smoked per day. This is recorded as pack-year history (packages per day × years smoked). For example, if a patient smoked two packs a day for 20 years, the patient has a 40 pack-year history. Determine exposure to secondhand smoke, because any form of tobacco exposure increases a patient’s risk for cardiopulmonary diseases (American Lung Association [ALA], 2020a).
Respiratory infections.
Obtain information about the frequency and duration of a patient’s respiratory tract infections. Although everyone occasionally has a self-limiting cold, some people develop bronchitis or pneumonia. On average, patients have four colds per year. Determine if and when a patient has had a pneumococcal or influenza (flu) vaccine. This is especially important when assessing older adults because of their increased risk for respiratory disease (Touhy and Jett, 2018). Ask about any known exposure to tuberculosis (TB) and the date and results of the last tuberculin skin test.
Determine a patient’s risk for human immunodeficiency virus (HIV) infection. Patients with a history of intravenous (IV) drug use and multiple unprotected sex partners are at risk of developing HIV infection. Patients do not always display symptoms of HIV infection until they present with Pneumocystis or Mycoplasma pneumonia. Patients with HIV/AIDS (acquired immunodeficiency syndrome) or other immunocompromised states are at increased risk for respiratory infections (McCance and Huether, 2019).
The COVID-19 pandemic poses increased health risks. While people of any age, even healthy young adults, can get this virus, the risk for severe illness increases with age, with older adults at highest risks. People with underlying medical conditions, such as but not limited to cancer, chronic cardiopulmonary illness, immunosuppression, obesity, diabetes, or Down syndrome, also have an increased risk for severe illness. This is an easily transmissible respiratory infection by respiratory droplets and airborne transmission; it commonly spreads during close contact. Initial symptoms are similar to influenza, but this virus spreads more efficiently than influenzas (CDC, 2021d).
Allergies.
Inquire about your patient’s exposure to airborne allergens (e.g., pet dander, pollen, or mold). Typical allergy symptoms include watery eyes, sneezing, runny nose, or respiratory symptoms such as cough or wheezing. When obtaining information from the patient, ask specific questions about the type of allergens, response to these allergens, and successful and unsuccessful relief measures. In addition, determine the effect of environmental air quality and secondhand smoke exposure on the patient’s allergy and symptoms. Safe nursing practice also includes obtaining information about food, drug, or insect sting allergies on the initial history and physical. However, always double-check this information with the patient on subsequent assessments, especially concerning respiratory allergens (Ball et al., 2019).
Medications.
Another component of the nursing history includes determining all the medications that a patient is using. These include prescribed medications, over-the-counter medications, folk medicine, herbal medicines, alternative therapies, and illicit drugs and substances. Some of these preparations have adverse effects by themselves or because of interactions with other drugs (Ball et al., 2019). For example, a person using a prescribed bronchodilator drug may choose to use an over-the-counter inhalant as well. Many of these contain ephedrine or ma huang, a natural ephedrine, which acts like epinephrine. This product reacts with the prescribed medication by potentiating or decreasing the effect of the prescribed medication. Patients taking warfarin for blood thinning prolong the prothrombin time (PT)/international normalized ratio (INR) results if they are taking ginkgo biloba, garlic, or ginseng with the anticoagulant. The drug interaction can precipitate life-threatening bleeding, such as gastrointestinal bleeding (Harding et al., 2020).
It is important to determine whether a patient uses illicit drugs. Inhaled opioids, which are often diluted with talcum powder, cause pulmonary disorders resulting from the irritant effect of the powder on lung tissues. Marijuana is usually smoked in the form of a joint or pipe. Marijuana smoke is an irritant to the lungs, putting users at higher risk for respiratory illnesses (NIDA, 2019). Cocaine is snorted through the nose, placed on the gums, smoked, or injected. Cocaine abusers can have acute cardiovascular changes such as constricted blood vessels and increased heart rate and blood pressure. People who use the inhaled form of cocaine often develop respiratory infections such as pneumonia. Cocaine deaths are often caused by heart attack or stroke (NIDA, 2018).
As with all medications, assess a patient’s knowledge and ability to self-administer medications correctly (see Chapter 31). It is especially important to assess that your patient understands the potential side effects of medications. Patients need to recognize adverse reactions and be aware of the dangers in combining prescribed medications with over-the-counter drugs.
Physical examination.
The physical examination includes assessment of the cardiopulmonary system (see Chapter 30). Give special consideration when assessing an older adult patient for changes that occur with the aging process (Table 41.1). These changes affect the patient’s activity tolerance and level of fatigue or cause transient changes in vital signs and are not always associated with a specific cardiopulmonary disease. Use clinical judgment to ensure appropriate analysis of assessment data.
Inspection includes observing the nails for clubbing (see Chapter 30). Clubbed nails often occur in patients with chronic oxygen deficiency, such as cystic fibrosis and congenital heart defects. Also note the shape of the chest wall. Conditions such as advancing age and chronic obstructive pulmonary disease (COPD) cause the chest to assume a rounded “barrel” shape (Ball et al., 2019; Harding et al., 2020).
Observe chest wall movement for retraction (e.g., sinking in of soft tissues of the chest between the intercostal spaces) and use of accessory muscles. Elevation of a patient’s clavicles at rest reveals increased work of breathing. Also observe the patient’s breathing pattern and assess for paradoxical breathing (the chest wall contracts during inspiration and expands during exhalation) or asynchronous breathing. At rest, the normal adult respiratory rate is 12 to 20 breaths/min. Bradypnea is less than 12 breaths/min, and tachypnea is greater than 20 breaths/min (see Chapter 29). In some conditions, such as metabolic acidosis, the acidic pH stimulates an increase in rate, usually greater than 35 breaths/min, and depth of respirations (Kussmaul respiration) to compensate by decreasing carbon dioxide levels. Apnea is the absence of respirations for 15 to 20 seconds or longer. Cheyne-Stokes respiration occurs when there is decreased blood flow or injury to the brainstem. This type of breathing is an abnormal respiratory pattern, with periods of apnea followed by periods of deep breathing and then shallow breathing followed by more apnea (McCance and Huether, 2019; Harding et al., 2020).
Palpation.
Palpation of the chest provides assessment data in several areas. It documents the type and amount of thoracic excursion; elicits any areas of tenderness; and helps to identify tactile fremitus, thrills, heaves, and the cardiac point of maximal impulse (PMI). Palpation of the extremities provides data about the peripheral circulation (e.g., the presence and quality of peripheral pulses, skin temperature, color, and capillary refill) (see Chapter 30).
Palpation of the feet and legs determines the presence or absence of peripheral edema. Patients with alterations in cardiac function, such as those with heart failure or hypertension, often have pedal or lower-extremity edema. Edema is graded from 1+ to 4+, depending on the depth of visible indentation after firm finger pressure (see Chapter 30).
Palpate the pulses in the neck and extremities to assess arterial blood flow (see Chapter 30). Use a scale of 0 (absent pulse) to 4+ (full, bounding pulse) to describe what you feel. The normal pulse is 2+; a weak, thready pulse is 1+. Never palpate both carotid arteries at the same time as doing so may cause the patient to lose consciousness (Ball et al., 2019).
Percussion.
Percussion detects the presence of abnormal fluid or air in the lungs. It also determines diaphragmatic excursion (see Chapter 30).
Auscultation.
Auscultation identifies the presence of normal and abnormal heart and lung sounds (see Chapter 30). Auscultation of the cardiovascular system includes assessing for normal S1 and S2 sounds and the presence of abnormal S3 and S4 sounds (gallops), murmurs, or rubs. Identify the location, intensity, pitch, and quality of a murmur. Auscultation also identifies any bruits over the carotid, abdominal aorta, and femoral arteries (Ball et al., 2019).
“Adventitious breath sounds” is another term for abnormal breath sounds. They include wheezing, crackles, and rhonchi. Wheezing is a continuous, high-pitched musical sound caused by high-velocity movement of air through a narrowed airway. It is associated with asthma, acute bronchitis, or pneumonia. It occurs during inspiration, expiration, or both. Determine whether there are any precipitating factors, such as respiratory infection, allergens, exercise, or stress. Crackles are discontinuous sounds of various pitch most often heard during inspiration. They are a result of the disruption of the small respiratory passages and cannot be cleared by coughing. They are often heard in patients with pneumonia or emphysema or chronic bronchitis. Rhonchi, or sonorous wheezes, are deeper sounding in pitch than crackles and are often heard during expiration. They reflect the presence of thick secretions or muscle spasms in the airway. Rhonchi can often be cleared by coughing and are most commonly heard in patients with asthma or pneumonia (Ball et al., 2019).
Diagnostic tests.
A variety of diagnostic tests are used to monitor and assess cardiopulmonary function. Some of these tests are noninvasive, while others are more invasive. Diagnostic testing used in the assessment and evaluation of the patient with cardiopulmonary alterations is summarized in Tables 41.3 through 41.5. When reviewing results of pulmonary function studies, be aware of expected variations in patients from different cultures
Inspection includes observing the nails for clubbing (see Chapter 30). Clubbed nails often occur in patients with chronic oxygen deficiency, such as cystic fibrosis and congenital heart defects. Also note the shape of the chest wall. Conditions such as advancing age and chronic obstructive pulmonary disease (COPD) cause the chest to assume a rounded “barrel” shape (Ball et al., 2019; Harding et al., 2020).
Observe chest wall movement for retraction (e.g., sinking in of soft tissues of the chest between the intercostal spaces) and use of accessory muscles. Elevation of a patient’s clavicles at rest reveals increased work of breathing. Also observe the patient’s breathing pattern and assess for paradoxical breathing (the chest wall contracts during inspiration and expands during exhalation) or asynchronous breathing. At rest, the normal adult respiratory rate is 12 to 20 breaths/min. Bradypnea is less than 12 breaths/min, and tachypnea is greater than 20 breaths/min (see Chapter 29). In some conditions, such as metabolic acidosis, the acidic pH stimulates an increase in rate, usually greater than 35 breaths/min, and depth of respirations (Kussmaul respiration) to compensate by decreasing carbon dioxide levels. Apnea is the absence of respirations for 15 to 20 seconds or longer. Cheyne-Stokes respiration occurs when there is decreased blood flow or injury to the brainstem. This type of breathing is an abnormal respiratory pattern, with periods of apnea followed by periods of deep breathing and then shallow breathing followed by more apnea (McCance and Huether, 2019; Harding et al., 2020).
Palpation.
Palpation of the chest provides assessment data in several areas. It documents the type and amount of thoracic excursion; elicits any areas of tenderness; and helps to identify tactile fremitus, thrills, heaves, and the cardiac point of maximal impulse (PMI). Palpation of the extremities provides data about the peripheral circulation (e.g., the presence and quality of peripheral pulses, skin temperature, color, and capillary refill) (see Chapter 30).
Palpation of the feet and legs determines the presence or absence of peripheral edema. Patients with alterations in cardiac function, such as those with heart failure or hypertension, often have pedal or lower-extremity edema. Edema is graded from 1+ to 4+, depending on the depth of visible indentation after firm finger pressure (see Chapter 30).
Palpate the pulses in the neck and extremities to assess arterial blood flow (see Chapter 30). Use a scale of 0 (absent pulse) to 4+ (full, bounding pulse) to describe what you feel. The normal pulse is 2+; a weak, thready pulse is 1+. Never palpate both carotid arteries at the same time as doing so may cause the patient to lose consciousness (Ball et al., 2019).
Percussion.
Percussion detects the presence of abnormal fluid or air in the lungs. It also determines diaphragmatic excursion (see Chapter 30).
Auscultation.
Auscultation identifies the presence of normal and abnormal heart and lung sounds (see Chapter 30). Auscultation of the cardiovascular system includes assessing for normal S1 and S2 sounds and the presence of abnormal S3 and S4 sounds (gallops), murmurs, or rubs. Identify the location, intensity, pitch, and quality of a murmur. Auscultation also identifies any bruits over the carotid, abdominal aorta, and femoral arteries (Ball et al., 2019).
“Adventitious breath sounds” is another term for abnormal breath sounds. They include wheezing, crackles, and rhonchi. Wheezing is a continuous, high-pitched musical sound caused by high-velocity movement of air through a narrowed airway. It is associated with asthma, acute bronchitis, or pneumonia. It occurs during inspiration, expiration, or both. Determine whether there are any precipitating factors, such as respiratory infection, allergens, exercise, or stress. Crackles are discontinuous sounds of various pitch most often heard during inspiration. They are a result of the disruption of the small respiratory passages and cannot be cleared by coughing. They are often heard in patients with pneumonia or emphysema or chronic bronchitis. Rhonchi, or sonorous wheezes, are deeper sounding in pitch than crackles and are often heard during expiration. They reflect the presence of thick secretions or muscle spasms in the airway. Rhonchi can often be cleared by coughing and are most commonly heard in patients with asthma or pneumonia (Ball et al., 2019).
Diagnostic tests.
A variety of diagnostic tests are used to monitor and assess cardiopulmonary function. Some of these tests are noninvasive, while others are more invasive. Diagnostic testing used in the assessment and evaluation of the patient with cardiopulmonary alterations is summarized in Tables 41.3 through 41.5. When reviewing results of pulmonary function studies, be aware of expected variations in patients from different cultures
Setting priorities.
A patient’s level of health, age, lifestyle, and environmental risk factors affect tissue oxygenation. Patients with severe impairments in oxygenation have multiple priorities of care. Use your clinical judgment to determine which outcome is the highest priority. For example, in an acute care setting, maintaining a patent airway has a higher priority than improving the patient’s exercise tolerance. The need for a patent airway is immediate; as the patient’s level of oxygen improves, activity tolerance increases (Urden et al., 2020). In a second example, when caring for a patient who has an abdominal incision, pain control is a priority. In this situation, controlling the patient’s pain facilitates coughing and deep breathing and activity (Harding et al., 2020). However, in a community-based or primary care setting, priorities often focus on primary or tertiary health promotion activities, such as smoking cessation, exercise, and/or diet modifications.
Both you and your patient need to focus on the same expected outcomes. In addition to individualizing each outcome, be sure that the outcomes are realistic, have reasonable time frames, and are attainable for the patient. Be sure to respect the patient’s preferences for the degree of active engagement in the care process. Some patients will choose to be very active and desire to make day-to-day decisions. Others may choose to assume a more passive role, preferring that you choose a course of action while keeping them informed (Harding et al., 2020).
Teamwork and collaboration.
The time spent with a patient in any setting is limited. Therefore, collaborate with family members, colleagues, and other health care specialists to achieve the established expected outcomes. Some patients need to improve their exercise and activity tolerance; for other patients, continuing care involves participating in a community-based cardiopulmonary rehabilitation program. Some patients need home physical therapy.
Collaboration with physical therapists, nutritionists, respiratory therapists, and community-based nurses is valuable for patients with heart failure or chronic lung conditions. These professionals work with patients and their caregivers using resources in the community to assist them in attaining and maintaining the highest possible level of wellness. In addition, professionals identify community resources and support systems to help prevent and manage symptoms related to cardiopulmonary diseases. Communication among everyone on the patient’s health care team and recognition of everyone’s contributions in achieving the health care outcomes for the patient are imperative.
John’s priorities of care for Mr. Edwards are to improve his airway clearance and gas exchange. John plans interventions to teach Mr. Edwards effective coughing techniques, to position him in semi-Fowler’s to high Fowler’s position, to maintain hydration, and to begin ambulation. As Mr. Edwards’ airway clearance improves, his gas exchange will improve, and his dyspnea and oxygen saturation will also improve.
John knows that Mr. and Mrs. Edwards’ smoking history poses risks for respiratory disease, but Mr. Edwards has the greatest risk. As Mr. Edwards improves, John wants to learn Mr. and Mrs. Edwards’ understanding of how smoking affects Mr. Edwards’ health. Information about smoking cessation may be useful if they are receptive. He knows from experience that acute care issues need to be resolved before a patient can benefit from patient education.
Implementation
There are interventions for promoting and maintaining adequate oxygenation across the continuum of care. As a nurse, you use clinical judgment to determine which interventions are appropriate for your patients. You will be responsible for independent interventions such as positioning, coughing techniques, and health education for disease prevention. In addition, you will provide physician-initiated interventions such as oxygen therapy, lung inflation techniques, and chest physiotherapy.
Health promotion.
Maintaining a patient’s optimal level of health reduces the number and/or severity of respiratory symptoms. Prevention of respiratory infections is foremost in maintaining optimal health (Box 41.6). Providing cardiopulmonary-related health information is an important nursing responsibility.
Healthy lifestyle.
Identification and elimination of risk factors for cardiopulmonary disease are important parts of primary care. The risk factors for cardiac disease are lower when total cholesterol levels are less than 200 mg/dL, high-density lipoprotein (HDL) levels are greater than 40 mg/dL in men and 50 mg/dL in women, and low-density lipoprotein (LDL) levels are less than 160 mg/dL (Harding et al., 2020). Encourage patients to eat a healthy low-fat, high-fiber diet and maintain a body weight in proportion to their height (see Chapter 45). The Dietary Approaches to Stop Hypertension (DASH) diet, along with exercise, stress reduction, and limiting alcohol intake, has been shown to decrease a patient’s risk of hypertension (NHLBI, n.d.a). Eliminating cigarettes and other tobacco use and adequately hydrating are additional healthy behaviors. Encourage patients to examine their habits and make appropriate changes. Patients with cardiopulmonary alterations need to minimize their risk for infection, especially during the winter months (see Box 41.6).
Exercise is a key factor in promoting and maintaining a healthy heart and lungs. Encourage patients to have at least 150 minutes a week of moderate intensity exercise and at least 2 days a week of muscle-strengthening activity (USDHHS, 2018). Aerobic exercise is necessary to improve lung and heart function and strengthen muscles. Walking is an efficient way to achieve a good aerobic workout. Many shopping malls allow people to walk in the enclosed mall before the shops open. During the hot summer months, teach patients to limit activities to early in the day or late in the evening, when temperatures are lower. In addition, teach the importance of maintaining adequate hydration and sodium intake, especially if they are taking diuretics. Caution patients with known cardiac disease and those with multiple risk factors to avoid exertion in cold weather. Shoveling snow is especially risky and often precipitates a cardiac event. Other activities, such as hanging holiday lights and decorations in the extreme cold, can precipitate chest pain and bronchospasm. Please refer to Chapter 38 for further discussion on activity and exercise.
Environmental pollutants.
Avoiding exposure to secondhand smoke is essential to maintaining optimal cardiopulmonary function (ALA, 2020a). Most public places, such as businesses or restaurants, ban smoking or have separate areas designated as smoking areas. Provide counseling and support so that a patient who lives with secondhand smoke in the home understands its effects. If the patient is smoking and wants to quit, encourage the patient’s family to support the patient in the attempt to quit.
Help patients develop a plan to avoid environmental hazards in their home or work environments when possible. For example, teach patients who know that pollen triggers an asthma exacerbation to keep windows closed and use air filters when air pollen counts are high (Hockenberry et al., 2019; Harding et al., 2020). Many health care agency dress codes prohibit the use of perfumes or colognes because they often affect patient breathing patterns and allergies. People in some occupations, such as farming, painting, and carpentry, may benefit from the use of particulate filter masks to reduce the inhalation of particles.
Acute care.
Patients with acute pulmonary illnesses require nursing interventions directed toward halting the pathological process (e.g., respiratory tract infection), shortening the duration and severity of an illness (e.g., hospitalization with pneumonia), and preventing complications from the illness or treatments (e.g., hospital-acquired infection resulting from invasive procedures) (Harding et al., 2020; Urden et al., 2020).
Dyspnea management.
Dyspnea is difficult to treat. Health care providers individualize treatments for each patient and usually implement more than one therapy. Treatment of the underlying process causing dyspnea is then followed with other therapies (e.g., pharmacological measures, oxygen therapy, physical techniques, and psychosocial techniques). Pharmacological agents include bronchodilators, inhaled steroids, mucolytics, and low-dose antianxiety medications. Oxygen therapy reduces dyspnea associated with exercise and hypoxemia. Physical and psychological techniques such as cardiopulmonary reconditioning (e.g., exercise, breathing techniques, and cough control), relaxation techniques, biofeedback, and meditation are also beneficial (Harding et al., 2020).
Airway maintenance.
The airway is patent when the trachea, bronchi, and large airways are free from obstructions. Airway maintenance requires adequate hydration to prevent thick, tenacious secretions. Proper coughing techniques remove secretions and keep the airway open. A variety of interventions such as suctioning, chest physiotherapy, and nebulizer therapy assist patients in managing alterations in airway clearance (Urden et al., 2020).
Mobilization of pulmonary secretions.
The ability of a patient to mobilize pulmonary secretions makes the difference between a short-term illness and an illness involving a long recovery with complications. Nursing interventions promoting removal of pulmonary secretions such as repositioning and suctioning assist in achieving and maintaining a clear airway and help to promote lung expansion and gas exchange (Mendes et al., 2019; Strickland et al., 2013; Strickland, 2015).
Hydration.
Maintenance of adequate systemic hydration keeps mucociliary clearance normal. In patients with adequate hydration, pulmonary secretions are thin, white, watery, and easily removable with minimal coughing. Excessive coughing to clear thick, tenacious secretions is fatiguing and energy depleting. It can also cause pain in the chest muscles and ribs, which further decreases the patient’s ability to cough and clear secretions. The best way to maintain thin secretions is to provide a fluid intake of 1500 to 2500 mL/day unless contraindicated by cardiac or renal status. The color, consistency, and ease of mucus expectoration determines adequacy of hydration (Harding et al., 2020).
Humidification.
Humidification is the process of adding water to gas to keep airways moist. It is necessary for patients receiving oxygen therapy at high flow rates, typically greater than 4 L/minute (see agency protocols). Oxygen humidification via nasal cannula or face mask is achieved by bubbling oxygen through sterile water (see Skill 41.4). Sterile water should be used to decrease the risk of hospital-acquired infection; follow agency protocols to change the solution (Wen et al., 2017).
When caring for pediatric patients, humidity may be applied to all oxygen devices, regardless of flow rates. Infants and children have smaller airways than adults, and secretions are more likely to obstruct airways in the younger population. Humidity is added to help ease the ability of infants and children to clear their airways (ATS, 2019; Walsh and Smallwood, 2017).
Nebulization.
Nebulization adds moisture to inspired air by mixing particles of varying sizes with the air. Aerosolization suspends the maximum number of water drops or particles of the desired size in inspired air. When the thin layer of fluid supporting the mucous layer over the cilia dries, the cilia are damaged and unable to adequately clear the airway. Humidification through nebulization enhances mucociliary clearance, the natural mechanism of the body for removing mucus and cellular debris from the respiratory tract. This, in turn, improves the clearance of pulmonary secretions. Nebulization is also a method of administration for certain medications, such as bronchodilators and mucolytic agents (Harding et al., 2020).
Coughing and deep-breathing techniques.
Coughing is an effective technique for maintaining a patent airway. Deep-breathing exercise with coughing is an airway clearance maneuver that is effective when spontaneous coughing is inadequate (Hanada et al., 2020; Eltorai et al., 2018). It permits a patient to remove secretions from both the upper and lower airways. The normal series of events in the directed cough is deep inhalation, closure of the glottis, active contraction of the expiratory muscles, and glottis opening. Deep inhalation increases the lung volume and airway diameter, allowing the air to pass through partially obstructing mucous plugs or other foreign matter. Contraction of the expiratory muscles against the closed glottis causes a high intrathoracic pressure to develop. When the glottis opens, a large flow of air is expelled at a high speed, providing momentum for mucus to move to the upper airways, allowing a patient to expectorate or swallow it.
The huff cough stimulates a natural cough reflex and is generally used to help move secretions to the larger airways. The patient inhales deeply and then holds the breath for 2 to 3 seconds. While forcefully exhaling, the patient opens the glottis by saying the word huff. With practice the patient inhales more air and is able to progress to the cascade cough. When using a cascade cough, the patient takes a slow, deep breath, holds it for 1 to 2 seconds, then opens the mouth and performs a series of coughs throughout exhalation. This technique is often used in patients with large amounts of sputum, such as those with cystic fibrosis (CFF, n.d.b).
The quad cough, or manually assisted cough technique, is for patients without abdominal muscle control, such as those with spinal cord injuries. While the patient breathes out with a maximal expiratory effort, the patient or nurse pushes inward and upward on the abdominal muscles toward the diaphragm, causing the cough (Chatwin et al., 2018).
Diaphragmatic breathing is a technique that encourages deep nasal inspiration to increase air flow to the lower lungs. The diaphragm descends (belly moves out) when breathing in and ascends (belly sinks in) when breathing out. For patients with COPD, this technique increases the patient’s tidal volume and oxygen saturation, reduces dyspnea, and improves exchange of respiratory gases (Mendes et al., 2019).
Encourage patients with chronic pulmonary diseases, upper respiratory tract infections, and lower respiratory tract infections to deep-breathe and cough at least every 2 hours while awake. Encourage patients with a large amount of sputum to cough every hour while awake. After some surgeries, it is recommended that patients perform deep breathing and coughing techniques every 2 to 4 hours while awake to prevent accumulation of secretions. Offer postoperative patients support devices (folded blanket, pillow, or palmed hands) to splint an abdominal or thoracic incision to minimize pain during directed coughing. Cough is a source of droplet transmission of pulmonary pathogens; thus, the health care provider should follow Standard Precautions (Harding et al., 2020).
Chest physiotherapy.
Chest physiotherapy (CPT) is external chest wall manipulation using percussion, vibration, or high-frequency chest wall compression (HFCWC) (Fig. 41.7). It is often used in conjunction with postural drainage and can help mobilize pulmonary secretions in a select group of patients. Box 41.7 describes the guidelines to determine whether CPT is indicated. Because there is no evidence to support its routine use in all patient populations, the American Association for Respiratory Care (AARC) does not support the routine use of CPT with all patients. Instead CPT is used for patients with retained secretions who cannot expectorate those secretions, such as patients with cystic
Postural drainage is a component of pulmonary hygiene; it consists of drainage, positioning, and turning and is sometimes accompanied by chest percussion and vibration. It aids in improving secretion clearance and oxygenation. Positioning involves draining affected lung segments (Table 41.6) and helps to drain secretions from those segments of the lungs and bronchi into the trachea. Some patients do not require postural drainage of all lung segments. Clinical assessment is crucial in identifying specific lung segments requiring it. For example, patients with left lower lobe atelectasis require postural drainage of only the affected region, whereas a child with CF often requires postural drainage of all lung segments
Maintenance and promotion of lung expansion.
Nursing interventions to maintain or promote lung expansion include noninvasive techniques such as ambulation, positioning, and incentive spirometry.
Ambulation.
Immobility is a major factor in developing atelectasis, ventilator-associated pneumonia (VAP), and functional limitations, including muscle weakness and fatigue (Nuwi and Irwan, 2018). This decline in status is often referred to as deconditioning. Early-ambulation studies indicate that the therapeutic benefits of activity include an increase in general strength and lung expansion. Even the patient who requires invasive mechanical ventilation benefits by an early-mobility program. Such mobility programs should include input from both respiratory and physical therapists in the treatment plan. Progressive mobilization from dangling the legs to standing and then walking is safe for intubated patients (Hartjes, 2018) (see Chapter 38).
Positioning.
A person who is healthy and completely mobile maintains adequate ventilation and oxygenation by frequent position changes during daily activities. However, when a person’s illness or injury restricts mobility, the risk for respiratory impairment increases. Frequent changes of position are simple and cost-effective methods for reducing stasis of pulmonary secretions and decreased chest wall expansion, both of which increase the risk of pneumonia.
The 45-degree semi-Fowler’s position is the most effective to promote lung expansion and reduce pressure from the abdomen on the diaphragm. When a patient is in this position, be sure that the patient does not slide down in bed, which can reduce lung expansion. Sliding also increases the risk of pressure injuries. Position a patient with unilateral lung disease, such as pneumothorax, atelectasis, or pneumonia of one lung, in a manner to promote perfusion of the healthy lung and improve oxygenation. In most cases, you position the patient with the good lung down. The majority of patients with COVID-19 who develop ARDS and are mechanically ventilated improve their oxygenation in the prone position, likely due to a better ventilation-perfusion matching (Langer et al., 2021). In the presence of pulmonary abscess or hemorrhage, position the patient with the affected lung down to prevent drainage toward the healthy lung.
Incentive spirometry.
Incentive spirometry encourages voluntary deep breathing by providing visual feedback to patients about inspiratory volume. It is a commonly used intervention that promotes deep breathing and is thought to prevent or treat atelectasis in the postoperative patient. Recent evidence suggests that the use of the incentive spirometer is not as effective at preventing postoperative pulmonary complications as it once was thought to be. The AARC recommends that its use be reserved for patients with existing atelectasis or those with risk factors for developing atelectasis, such as those who have undergone thoracic or abdominal surgery, patients with prolonged bed rest, or patients with neuromuscular disease or spinal cord injuries (Eltorai et al., 2018).
There are two types of incentive spirometers. Flow-oriented incentive spirometers consist of one or more plastic chambers that contain freely moving colored balls. A patient inhales slowly and with an even flow to elevate the balls and keep them floating as long as possible to ensure a maximally sustained inhalation. Volume-oriented incentive spirometry devices have a bellows that is raised to a predetermined volume by an inhaled breath (Fig. 41.11). An achievement light or counter provides visual feedback. Some devices are constructed so the light does not turn on unless the bellows is held at a minimum desired volume for a specified period to enhance lung expansion