Chapter 26: Vital Signs Lecture Notes

Introduction to Vital Signs

• Vital signs are essential clinical measurements that provide data regarding a patient’s health status. The core measurements encompass:     - Temperature (T)     - Pulse (P)     - Respiration (R)     - Blood pressure (BP)
• Frequently, two additional measurements are categorized with the primary vital signs:     - Pain: Often referred to as the "fifth sign."     - Pulse oximetry: Measurement of arterial oxygen saturation.

Indications for Vital Sign Assessment

• Vital signs must be assessed and documented in the following circumstances:     - Upon admission to any healthcare facility or institution to establish a baseline.     - According to established facility or institutional policies and procedures.     - Any time a change in the patient's condition is observed or suspected.     - Any time there is a loss of consciousness.     - Prior to and following any surgical or invasive diagnostic procedure.     - Prior to and following activities that may increase patient risk, such as the initial ambulation after surgery.     - Prior to the administration of medications that specifically affect cardiovascular and respiratory function.

Normal Standard Ranges for Healthy Adults

• Oral Temperature: Ranges from $35.8^{\circ}\text{C}$ to $37.5^{\circ}\text{C}$ (equivalent to $96.4^{\circ}\text{F}$ to $99.5^{\circ}\text{F}$).
• Pulse Rate: Ranges from $60$ to $100\,\text{beats/min}$, with an average of $80\,\text{beats/min}$.
• Respirations: Ranges from $12$ to $20\,\text{breaths/min}$.
• Blood Pressure: Normal levels are defined as being less than $120/80\,\text{mm Hg}$.

Body Temperature: Heat Production and Regulation

• The primary source of heat production in the body is metabolism.
• Metabolic rates are increased by various factors:     - Hormonal influences.     - Muscle movements.     - Physical exercise.
• Specific regulators of heat production include:     - Catecholamines: Epinephrine and norepinephrine are released when additional heat is required. These hormones alter metabolism to increase heat output.     - Thyroid Hormone: Increases metabolic activity and heat production over a longer term.     - Shivering: Involuntary muscle contractions that serve to increase heat production.
• The relationship between energy and heat: As energy production decreases, heat production tends to increase to maintain homeostasis.

Mechanisms of Heat Loss and Transfer

• Sources of Heat Loss:     - Skin: The primary source of heat loss from the body.     - Evaporation: The loss of heat through the evaporation of sweat.     - Respiration: Warming and humidifying inspired air results in heat loss.     - Elimination: The process of eliminating urine and feces.
• Transfer of Body Heat to the External Environment:     - Radiation: The diffusion or dissemination of heat by electromagnetic waves (e.g., heat lost from an uncovered head in cold weather).     - Convection: The dissemination of heat by motion between areas of unequal density (e.g., a fan blowing air over the skin).     - Evaporation: The conversion of a liquid (sweat) to a vapor.     - Conduction: The transfer of heat to another object via direct contact (e.g., sitting on a cold metal chair).

Factors Affecting Body Temperature

• Circadian Rhythms: Biological cycles that recur at approximately $24$-hour intervals, causing natural fluctuations in temperature.
• Age and Gender: Physiological differences across the lifespan and between sexes affect baseline temperature.
• Physical Activity: Increased exertion leads to increased muscle metabolism and heat production.
• State of Health: Presence of disease or infection can alter the set point for body temperature.
• Environmental Temperature: Extreme heat or cold in the surroundings can affect the body's ability to maintain a stable internal temperature.

Classification and Patterns of Fever (Pyrexia)

• Afebrile: A state where the patient is without a fever.
• Pyrexia (Febrile): A state where the patient has a fever.
• Types of Fever Patterns:     - Intermittent Fever: The body temperature returns to normal level at least once every $24$ hours.     - Remittent Fever: The temperature remains above normal and fluctuates several degrees up and down, but does not return to a normal range.     - Sustained (Continuous) Fever: The temperature remains consistently above normal with minimal variations.     - Relapsing (Recurrent) Fever: The temperature returns to normal for one or more days, followed by one or more episodes of fever that can last several days each.

Equipment and Sites for Temperature Assessment

• Equipment:     - Electronic and digital thermometers.     - Tympanic membrane thermometers.     - Disposable single-use thermometers.     - Temporal artery thermometers.     - Automated monitoring devices.
• Normal Temperatures for Healthy Adults by Site:     - Oral: $35.9^{\circ}\text{C} - 37.5^{\circ}\text{C}$ ($96.6^{\circ}\text{F} - 99.5^{\circ}\text{F}$).     - Rectal: $36.3^{\circ}\text{C} - 38.1^{\circ}\text{C}$ ($97.4^{\circ}\text{F} - 100.5^{\circ}\text{F}$).     - Axillary: $35.4^{\circ}\text{C} - 36.9^{\circ}\text{C}$ ($95.6^{\circ}\text{F} - 98.5^{\circ}\text{F}$).     - Tympanic: $36.8^{\circ}\text{C} - 38.3^{\circ}\text{C}$ ($98.2^{\circ}\text{F} - 100.9^{\circ}\text{F}$).     - Forehead (Temporal Artery): $36.3^{\circ}\text{C} - 38.1^{\circ}\text{C}$ ($98.7^{\circ}\text{F} - 100.5^{\circ}\text{F}$).

Pulse: Physiology and Regulation

• The pulse is regulated by the Autonomic Nervous System (ANS) through the cardiac sinoatrial (SA) node.
• Autonomic Regulation:     - Parasympathetic Stimulation: Decreases the heart rate.     - Sympathetic Stimulation: Increases the heart rate.
• Definition: The pulse rate equals the number of contractions measured over a peripheral artery in $1\,\text{minute}$.

Characteristics and Measurement of Peripheral Pulse

• Characteristics:     - Rate: Measured as normal, tachycardia (elevated rate), or bradycardia (slowed rate).     - Amplitude and Quality: Describes the strength of the pulse (e.g., strong, weak, or thready).     - Rhythm: The pattern of the beats and internal pauses.     - Stroke Volume: The actual volume of blood ejected from the heart with each individual heartbeat.
• Pulse Strength (Amplitude) Grading Scale:     - Grade 0: Pulse is absent; unable to palpate.     - Grade +1: Pulse is diminished; weaker than expected.     - Grade +2: Pulse is normal; brisk and expected.     - Grade 3+: Pulse is bounding.
• Sites for Detecting Pulse by Light Palpation:     - Temporal     - Carotid     - Brachial (located on the inside of the elbow)     - Radial (located on the wrist)     - Femoral (located in the groin)     - Popliteal (located behind the knee)     - Posterior tibial (located on the inner side of the ankle)     - Dorsalis pedis (located on the top of the foot)

Respiration: Physiology and Mechanics

• Ventilation: The mechanical movement of air in and out of the lungs.     - Inhalation: The act of breathing in.     - Exhalation: The act of breathing out.
• Diffusion: The exchange of oxygen ($O_2$) and carbon dioxide ($CO_2$) occurring between the alveoli of the lungs and the circulating blood.
• Perfusion: The exchange of oxygen and carbon dioxide between the circulating blood and the actual tissue cells.
• Control and Stimulants:     - Respiratory centers are located in the medulla and pons.     - These centers are activated by impulses from chemoreceptors.     - An increase in carbon dioxide ($CO_2$) level is the most powerful respiratory stimulant.

Terminology and Classification of Respiratory Patterns

• Eupnea: Normal, unlabored respiration. The ratio is typically one respiration for every four heartbeats ($1\text{:}4$).
• Tachypnea: Increased respiratory rate; often occurs due to an increased metabolic rate.
• Bradypnea: Decreased respiratory rate; often associated with specific pathologic conditions.
• Apnea: Periods during which no breathing occurs.
• Dyspnea: Difficult or labored breathing.
• Orthopnea: Changes in breathing difficulty that occur based on body position (e.g., needing to sit or stand to breathe comfortably).

Blood Pressure: Definitions and Physiology

• Blood pressure is the force exert by moving blood against the arterial walls.
• Systolic Pressure: The maximum pressure achieved when the left ventricle contracts and pushes blood through the aortic valve into the aorta (systole).
• Diastolic Pressure: The lowest pressure measured when the heart is at rest between beats (diastole).
• Pulse Pressure: The mathematical difference between the measured systolic and diastolic pressures.

Regulation and Influencing Factors of Blood Pressure

• Short-term Regulation:     - Neural: Mediated by the nervous system.     - Humoral: Pertaining to body fluids and hormonal controls.
• Physiological Factors:     - Cardiac Output: The strength and volume of heart contractions directly affect pressure levels.     - Vagus Nerve: Parasympathetic impulses from the vagus nerve slow the heart rate.     - Sympathetic Nervous System: Increases the heart rate to raise blood pressure.     - Baroreceptors: Located in the heart and arterial walls; they monitor pressure and signal the cardiovascular center in the brain.     - Renin–Angiotensin–Aldosterone System (RAAS): A hormone system that regulates blood pressure and fluid balance, resulting in an increase in pressure.
• Influencing Variables:     - Age and Race.     - Circadian rhythm.     - Biologic sex.     - Food intake and weight.     - Exercise and body position.     - Emotional state.     - Drugs and medications.

Abnormalities and Assessment of Blood Pressure

• Decreased Blood Pressure (Hypotension):     - Defined as a blood pressure reading less than $90/60\,\text{mm Hg}$.     - Can result from disease processes or be a side effect of medications.     - Indicates an inability of the body to maintain or return pressure to normal levels.
• Orthostatic Hypotension (Postural Hypotension):     - Results from an inadequate physiologic response to changes in body position.     - Occurs specifically when rising to an erect (standing) position.     - Common causes include dehydration, blood loss, or neurologic, cardiovascular, and endocrine system disorders.
• Assessment Equipment and Methods:     - Stethoscope and Sphygmomanometer (utilizing three sizes of cuffs: small, adult/medium, and large).     - Doppler ultrasound.     - Electronic/automated monitoring devices.
• Measurement Technique:     - Clinicians listen for Korotkoff sounds with a stethoscope.     - The first sound heard represents systolic pressure.     - The point where sounds change or cease represents diastolic pressure.     - Primary arteries used for assessment: Brachial artery and Popliteal artery.

Questions & Discussion

• Question #1: What is the term for the heat that is lost when a person goes out in the cold without a hat?     - Answer: B. Radiation.     - Rationale: Radiation is the diffusion or dissemination of heat by electromagnetic waves, such as occurs with an uncovered head. Convection involves motion between areas of unequal density. Evaporation is the conversion of liquid to vapor. Conduction involves direct contact with another object.
• Question #2: Tell whether the following statement is true or false: The normal pulse rate for adolescents and adults ranges from $60$ to $100\,\text{beats/min}$.     - Answer: A. True.     - Rationale: The standard normal range for adolescents and adults is indeed $60\text{--}100\,\text{beats/min}$.
• Question #3: Which pulse site is located on the inside of the elbow?     - Answer: D. Brachial.     - Rationale: The brachial site is on the inner elbow. The temporal site is on the side of the head, the radial site is on the wrist, and the femoral site is in the groin.
• Question #4: Tell whether the following statement is true or false: Changes in the rate and depth of inhalation and exhalation are brought about by the inhibition or stimulation of the respiratory muscles by respiratory centers in the medulla and pons.     - Answer: A. True.     - Rationale: The respiratory centers located in the medulla and pons are responsible for controlling the rate and depth of breathing via muscle stimulation or inhibition.