Pathophysiology Exam #4: An In-Depth Review of Pulmonary Function Alterations

Tidal volume

Volume of air exhaled after normal inspirations (500 mL)

Residual volume

Volume of air remaining in the lungs after maximum respiration (1200 mL)

Vital capacity

Maximal amount of air that can be moved in and out of the lungs with a single forced inspiration and expiration (4800 mL)

Forced expiratory volume in 1 second (FEV1)

Volume exhaled in the first second after deep inspiration and forced expiration

Forced vital capacity (FVC)

Total volume of air that the patient can forcibly exhale in one breath

The values of ____________ and ____________ are expressed as a percentage of the predicted normal for a person of the same sex, age, and height.

FEV1 and FVC (expressed as FEV1/FVC)

Describe how FEV1 and FVC (and their ratio) are affected in an obstructive pattern

- Reduced FEV1 (<80% of the predicted normal)

- Reduced FVC (but to a lesser extent than FEV1)

- FEV1/FVC ratio is reduced (<0.7)

Mild obstruction

- FEV1 is 80% or more of the predicted value

- If you have mild COPD, your spirometry test results can be normal after you take medication.

Moderate obstruction

FEV1 is 50-79% of the predicted value after medication

Severe obstruction

FEV1 is 30-49% of the predicted value after medication

Very severe obstruction

FEV1 is below 30% of the predicted value after medication

Describe how FEV1 and FVC (and their ratio) are affected in a restrictive pattern

- Reduced FEV1 (<80% of predicted normal)

- Reduced FVC (<80% of predicted normal)

- FEV1/FVC ratio is normal (>0.7)

Dyspnea

- Subjective sensation of uncomfortable breathing

- May not correlate with underlying disease

- Due to diffuse or focal disturbances in ventilation, gas exchange, or ventilation-perfusion

Severe dyspnea

- Flaring of the nostrils

- Use of accessory muscles of respiration

- Retraction of the intercostal spaces

Dyspnea on exertion

Shortness of breath with activity

Orthopnea

Dyspnea when lying down

Paroxysmal nocturnal dyspnea (PND)

- Awakening at night and gasping for air, must sit or stand up

- Heart failure and pulmonary disease

What is a cough?

Protective reflex that helps clear the upper airways; an explosive respiration

Irritant receptors in the airway are stimulated by...

- Particles

- Mucous

- Inflammation

- Foreign body

There are very _________ (few, many) irritant receptors in the distal airways (distal bronchi/alveaoli)

few; so we may have significant secretions in the distal airway without any cough initaited

Steps of the cough reflex

1.) Inspiration

2.) Closure of glottis and vocal cords

3.) Contraction of expiratory muscles

4.) Reopening of glottis

5.) Sudden forceful expiration (ideally removing particles/fb/mucous)

Effectiveness of a cough is depend on what 2 things?

- Depth of inspiration

- Degree of airway narrowing (more narrow = more velocity)

Stimulation of irritant receptors is transmitted to the CNS via the __________________ to the __________________.

vagus nerve; medulla

The cough reflex can be inhibited by...

- Opiates (codeine)

- Serotonergic agents (dextromethorphan)

Acute cough (time and causes)

Resolves in 2-3 weeks

Causes:

- URI, allergic rhinitis, acute bronchitis, pneumonia, CHF, PE, aspiration

Chronic cough (time and causes)

More than 3 weeks (>7-8 weeks)

Causes:

- Smoker: chronic bronchitis, cancer

- Nonsmoker: postnasal drip, non-asthmatic eosinophilic bronchitis, asthma, GERD, heightened cough reflex sensitivity, vocal cord dysfunction, medications

What does yellowish-green, cloudy, thick mucous indicate?

Bacterial infection

What does rusty or dark-colored sputum indicate?

Pneumococcal pneumonia

What does very large amounts of purulent sputum with foul odor indicate?

Bronchiectasis

What does thick, tenacious mucus indicate?

Asthma or cystic fibrosis

Blood-tinged sputum may result from ________________________ and may also be a sign of ______________ or ____________________________.

chronic cough; tumor; tuberculosis

Hemoptysis

- Coughing up bright red blood

- Frothy

- Alkaline pH

Eupnea

- Normal and effortless breathing

- 8-15 breaths per minute

- Tidal volume = 400-800 mL

Labored breathing is present if airway is...

obstructed

Large airway obstruction

- Slow ventilatory rate

- Increased effort

- Prolonged inspiration and expiration (stridor or wheeze)

Small airway obstruction

- Rapid ventilatory rate

- Small tidal volume

- Increased effort

- Prolonged expiration (wheezing)

- Asthma/COPD

Characteristics of restricted breathing

- Disorders that stiffen the lungs or chest wall and decrease compliance (fibrosis)

- Small tidal volumes

- Rapid ventilation rate

Tachypnea

Increased respiratory rate

Bradypnea

Decreased respiratory rate

Apnea

Absence of breathing

Hyperpnea

Normal rate, but deep respirations

Cheyne-Stokes

Gradual increases and decreases in respirations with periods of apnea

Biot's

Rapid, deep respirations (gasps) with short pauses between sets

Kussmaul's

Tachypnea and hyperpnea

Apneustic

Prolonged inspiratory phase with shortened expiratory phase

Minute ventilation =

tidal volume x respiratory rate

When alveolar ventilation is normal, CO2 is removed from the lungs _____________________________ as it is produced by cellular metabolism.

at the same rate

Normal arterial pressure of CO2

40 mmHg

Characteristics of hypoventilation

- Alveolar ventilation is inadequate in relationship to metabolic demands

- Leads to respiratory acidosis from hypercapnia (PaCO2 > 44 mmHg)

- Caused by airway obstruction, chest wall restriction, or altered neurologic control of breathing

- May be overlooked until severe

Characteristics of hyperventilation

- Alveolar ventilation exceeds the metabolic demands.

- Leads to respiratory alkalosis from hypocapnia (PaCO2 < 36 mmHg)

- Caused by anxiety, head injury, or severe hypoxemia

Cyanosis

- Bluish discoloration of the skin and mucous membranes

- 5g/dL of desaturated hemoglobin regardless of concentration

Characteristics of peripheral cyanosis

- Most often caused by poor circulation

- Best observed in the nail beds

- Ex: Reynauds

Characteristics of central cyanosis

- Caused by decreased arterial oxygenation (low partial pressure of oxygen)

- Best observed in buccal mucous membranes and lips

- Ex: pulmonary or cardiac disease (right to left shunts)

Clubbing is due to...

chronic hypoxia

Characteristics of pleural pain

- Usually sharp or stabbing in character

- Infection or inflammation of parietal pleura (pleuritis or pleurisy)

- Can cause pain when the pleura stretch during inspiration and are accompanied by a pleural friction rub (auscultation)

Characteristics of chest wall pain

- Muscle or rib pain (rib fracture)

- Costochondritis: inflammation of the costo-chondral junction

- Reproducible

Hypercapnia

- Increased carbon dioxide (CO2) in the arterial blood

(increased PaCO2) = respiratory acidosis

- Due to hypoventilation of alveoli

- CO2 easily diffuses from blood into alveolar space

- Occurs from decreased drive to breathe or an inadequate ability to respond to ventilatory stimulation

- Easily overlooked as breathing pattern and ventilation may appear normal

Hypoxemia

- Reduced oxygenation of arterial blood (reduced PaO2)

- Can lead to HYPOXIA – reduced oxygen of cells in tissues

Due to problems with:

- Oxygen delivery to alveoli

- Ventilation of alveoli

- Diffusion of oxygen from alveoli into blood

- Perfusion of pulmonary capillaries

Hypoxemia causes widespread ____________________________ and when severe leads to __________________________________.

tissue dysfunction; organ infarction

Hypoxemia due to decrease in oxygen delivery

- Depends on amount of oxygen in inspired air

Common clinical causes:

- High altitude

- Low oxygen content of gas mixture

- Enclosed breathing space (suffocation)

Hypoxemia due to hypoventilation of alveoli

- Hypoventilation causes increase in PaCO2 and decrease in PaO2

- Less oxygen available to diffuse into blood

- Can be corrected easily if alveolar ventilation is improved by increases in RATE and DEPTH of BREATHING

Hypoxemia due to diffusion of oxygen from alveoli into blood

Dependent on 2 factors:

1.) Balance between alveolar ventilation and perfusion (V/Q)

2.) Diffusion of oxygen across the alveolarcapillary membrane (impaired if membrane is thickened or if there is a decrease in SA)

V/Q Mismatch

Abnormal ventilation-perfusion ratio

Most common cause of hypoxemia

V/Q mismatch

Normally, the alveolar-capillary lung units receive ______________ amounts of ventilation and perfusion

equal

Normal VQ

0.8-0.9

- Perfusion is greater than ventilation in lung base

- Blood is normally shunted to bronchial circulation

Low V/Q

- Inadequate ventilation occurs to well perfused areas of the lung

- Atelectasis

- Asthma

- Pulmonary edema

- Pneumonia

Very low V/Q

SHUNTING

- Blood passes through portions of the pulmonary capillary bed that gets no ventilation

High V/Q

- Poor perfusion to well ventilated portions of the lung

- Wasted ventilation (alveolar dead space)

- PE

Hypoxemia due to poor perfusion of pulmonary capillaries

- Diffusion impaired due to thickening of the surface (edema, fibrosis)

- Surface area is decreased

- Emphysema (destruction of alveoli)

Characteristics of acute respiratory failure

- Gas exchange is inadequate (hypoxemia)

- PaO2 is ≤50 mm Hg.

- Hypercapnia occurs, during which partial pressure of carbon dioxide (PaCO2) is ≥50 mm Hg

- pH is ≤7.25

-Requires ventilatory support, oxygen, or both.–

-Often mix of hypercapnia and hypoxemia

-Complication of any major surgical procedure

- Most common post-op problems: atelectasis, pneumonia, pulmonary edema, PE

Respiratory failure can be due to direct injury to...

- Lungs

- Airway

- Chest wall

- Brain

- Liver

True or False: Only those with a history of pulmonary disease can have respiratory failure

False

Respiratory failure is mostly...

Hypercapnic: d/t poor alveolar ventilation (pt. needs ventilator support)

Hypoxemic: d/t poor exchange of oxygen between alveoli and capillaries (pt. needs oxygen therapy)

Early symptoms of hypoxia

Restlessness, anxiety, tachycardia/tachypnea

Late symptoms of hypoxia

Bradycardia, extreme restlessness, dyspnea

Causes of chest wall restriction

- Deformity

- Trauma

- Immobilization (pain, disease, fat tissue)

Work of breathing is increased and ventilation may be compromised d/t a decrease in tidal volume

Diagnosis of chest wall restriction

- Pulmonary function testing (look for reduced FVC)

- ABG (hypercapnia)

- Radiographs

Causes of neuromuscular disease

- Muscular dystrophy

- Myasthenia gravis

- GBS

Can lead to impairment of respiratory muscles d/t chest wall restrictions

____________________________ is the most common cause of hospital admission due to hypoventilation and ______________________.

Respiratory difficulty; hypercapnia

_________________________ is the instability of a portion of the chest wall from rib or sternal fracture.

Flail chest

Flail chest can cause ________________________________ of the chest with breathing, which can then lead to...

paradoxical movement; hypoxemia and hypoventilation

Pneumothorax

Presence of air or gas in the pleural space caused by a rupture in the visceral pleura or the parietal pleura and the chest wall

Primary (spontaneous) pneumothorax

Occurs unexpectedly in healthy individuals (men, 20-40 yoa)

Secondary pneumothorax

Caused by disease (COPD), trauma, injury (mechanical ventilation), or condition

Iatrogenic pneumothorax

Caused by medical treatments (transthoracic needle aspiration)

Open pneumothorax

Air pressure in the pleural space equals barometric pressure, because air that is drawn into the pleural space during inspiration is forced back out during expiration

Tension pneumothorax

- Site of pleural rupture acts as a one-way valve, permitting air to enter on inspiration but preventing its escape by closing up during expiration

- As more air enters, air pressure exceeds barometric pressure

- Air pressure pushes against the recoiled lung causing compression atelectasis, pushes against the mediastinum compressing and displacing the heart

LIFE THREATENING

Clinical manifestations of pneumothorax

- Sudden pleural pain, tachypnea, and possible mild dyspnea

- Severe hypoxemia, tracheal deviation away from the affected lung, and hypotension

- Absent or decreased breath sounds, hyper-resonance to percussion on affected side

Treatment: chest tube

Pleural effusion

Presence of fluid in the pleural space from blood vessels or lymphatics

Transudative effusion

Watery and diffuses out of the capillaries (CHF)

Exudative effusion

High concentrations of white blood cells and plasma proteins (inflammation/infection/CA)

Chylothorax

Milky fluid of lymph/fat (injury/infection/disorder)

Hemothorax

Blood exudate

Empyema

Pus (infection, inflammation, abcess)

Clinical manifestations of pleural effusion

- Dyspnea and pleural pain

- Small pleural effusions may be undetected and DO NOT affect lung function

Treatment: thoracocentesis, chest tube, surgery

Clinical manifestations of empyema

Cyanosis, fever, tachycardia, cough, and pleural pain

Treatment

-Administration of antimicrobial medications (Staph aureus, E.coli, anaerobic bacteria and Klebsiella pneumoniae)

- Drainage of the pleural space with a chest tube

Characteristics of restrictive lung disorders

- Decreased compliance of lung tissue

- Patients complain of dyspnea, have increased RR, decreased TV

- Decreased FVC; FEV1/FVC normal (<0.7)

- Low V/Q = hypoxemia

_________________________ is the passage of fluid and solid particles into the lungs.

Aspiration

Most frequent site affected by aspiration

Right lower lobe