Respiratory Disorders: Pathophysiology, Assessment & Gas Exchange

What is the clinical definition of dyspnea?

A subjective sensation reported by the patient of difficult, uncomfortable, or inadequate breathing.

Why does orthopnea occur when a patient with heart failure or advanced lung disease lies flat?

Gravitational fluid redistributes from the lower extremities toward the chest, increasing pulmonary pressure and work of breathing.

What is paroxysmal nocturnal dyspnea (PND)?

Sudden episodes of waking from sleep gasping for air due to nighttime fluid shifts into the pulmonary circulation.

How do clinicians differentiate an acute cough from a chronic cough based on duration?

An acute cough lasts less than 3 weeks; a chronic cough lasts longer than 6 weeks.

What is the term for coughing up blood or blood-tinged sputum?

Hemoptysis

What metabolic state causes Kussmaul respirations, and what is the body attempting to accomplish?

Metabolic acidosis; deep, labored breathing compensates by blowing off excess carbon dioxide.

What underlying pathology is indicated by Cheyne-Stokes respirations?

Impairment of the respiratory control center in the brainstem.

How does hypoventilation affect arterial CO2 levels and blood pH?

It causes CO2 buildup, leading to respiratory acidosis.

How does hyperventilation affect arterial blood gases?

Excessive ventilation blows off CO2, leading to respiratory alkalosis.

Which central nervous system signs develop as hypercapnia worsens?

Somnolence, confusion, lethargy, and progressively decreased level of consciousness.

What is the difference between hypoxemia and hypoxia?

Hypoxemia is low oxygen concentration in arterial blood; hypoxia is inadequate oxygen delivery to tissue cells.

How can a patient have severe tissue hypoxia despite normal arterial blood oxygen levels?

Impaired tissue perfusion prevents blood delivery to peripheral tissues.

What type of sign is cyanosis in terms of respiratory compromise?

Late, severe, and urgent.

What physiological condition causes digital clubbing?

Long-term, chronic tissue hypoxia.

In pulmonary physiology, what does ventilation describe?

The flow of air into and out of the alveoli.

In pulmonary physiology, what does perfusion describe?

The flow of blood through the pulmonary alveolar capillaries.

Why does severe pneumonia cause a ventilation-perfusion mismatch?

Alveoli are filled with inflammatory fluid, impairing ventilation.

Why does a pulmonary embolism cause a ventilation-perfusion mismatch?

A blood clot blocks blood flow to alveolar capillaries, impairing perfusion.

What defines acute respiratory failure?

Inability of the lungs to maintain adequate gas exchange.

Which early clinical cues indicate that a patient is developing impending respiratory failure?

Increased work of breathing, accessory muscle use, tachypnea, fatigue, anxiety, and altered mental status.

Why can a compensating patient with severe respiratory distress crash suddenly?

Respiratory muscle fatigue leads to rapid CO2 retention and cardiac arrest.

What mechanical defect defines restrictive lung disorders?

Inability of the lungs or chest wall to expand normally.

How does pulmonary fibrosis alter lung mechanics and gas exchange?

Scarring creates stiff, non-compliant lungs that resist inflation.

What mechanical defect defines obstructive lung disorders?

Airway narrowing or collapse that hinders airflow.

List three non-pulmonary conditions that cause chest wall restriction.

Severe obesity, chest wall skeletal deformities, and thoracic wall trauma.

What is flail chest, and what breathing motion characterizes it?

Fracture of consecutive ribs causing paradoxical movement.

Why does flail chest lead to hypoventilation?

Inefficient paradoxical chest expansion suppresses deep tidal breathing.

How does entry of air into the pleural space cause atelectasis?

It disrupts normal intrapleural negative pressure.

What structural mechanism makes a tension pneumothorax life-threatening?

A one-way valve effect prevents air escape during expiration.

How does a tension pneumothorax lead to cardiovascular collapse?

High intrapleural pressure compresses the vena cava.

How do transudative and exudative pleural effusions differ?

Transudates are watery fluids; exudates are protein/cell-rich fluids.

Differentiate empyema from chylothorax.

Empyema is infected pleural fluid; chylothorax is lymphatic fluid in the pleural space.

What is empyema?

Pus-filled pleural fluid from severe infection.

What is chylothorax?

Milky lymphatic fluid in the pleural space from thoracic duct trauma/obstruction.

What initial tissue reaction occurs when foreign material enters the lower airway during aspiration?

Acute pulmonary inflammation triggering chemical pneumonitis, mucosal injury, or aspiration pneumonia.

Differentiate obstructive atelectasis from compression atelectasis.

Obstructive atelectasis follows mucus/foreign body airway blockage; compression atelectasis occurs when external pleural fluid, air, or mass compresses lung tissue.

What structural airway abnormality characterizes bronchiectasis?

Chronic, irreversible dilation of the bronchi caused by repeated infection and inflammation.

What is the primary cause of pneumoconiosis?

Inhalation of inorganic dust particles causing chronic inflammation, tissue destruction, and pulmonary fibrosis.

What mechanism causes hypersensitivity alveolitis?

An immune-mediated reaction to repeated inhalation of organic dusts or fumes.

What primary microscopic membrane injury initiates acute respiratory distress syndrome (ARDS)?

Diffuse damage to the alveolar-capillary membrane.

What hallmark oxygenation finding strongly suggests ARDS rather than simple pulmonary edema?

Refractory hypoxemia.

Why do patients in advanced ARDS develop metabolic acidosis?

Severe systemic tissue hypoxia forces cells into anaerobic metabolism, generating high levels of lactic acid.

Which triad of pathophysiological changes narrows airways during an acute asthma attack?

Bronchial smooth muscle constriction, airway mucosal edema/inflammation, and hypersecretion of thick mucus.

What is status asthmaticus?

A severe, prolonged asthma exacerbation that does not respond to standard bronchodilator therapy.

How do beta-2 agonists and inhaled corticosteroids address distinct pathophysiological targets in asthma?

Beta-2 agonists relax constricted bronchial smooth muscle; corticosteroids suppress underlying chronic mucosal inflammation.

What two distinct lung pathologies combine to form COPD?

Chronic bronchitis and emphysema.

What primary tissue alteration causes persistent airway obstruction in chronic bronchitis?

Hypertrophy of submucosal mucus glands in bronchial walls.

What structural destruction causes air trapping in pulmonary emphysema?

Breakdown of alveolar walls and loss of pulmonary elastic recoil.

Why do patients with emphysema develop a barrel-chest configuration?

Chronic air trapping hyperinflates the lungs.

How do diagnostic imaging findings distinguish acute bronchitis from pneumonia?

Acute bronchitis shows clear lungs on chest X-ray; pneumonia shows alveolar infiltrates.

Why is pneumonia more likely than acute bronchitis to directly cause arterial hypoxemia?

Pneumonia infects and floods the alveoli with inflammatory exudate.

How does the immune system respond to initial Mycobacterium tuberculosis pulmonary infection?

It walls off the bacteria inside a granuloma/tubercle.

What does a positive tuberculin skin test signify?

Immune system exposure and sensitization to TB antigens.

Which clinical manifestations indicate active, contagious pulmonary tuberculosis?

Chronic productive cough, night sweats, low-grade afternoon fever, unexplained weight loss, and hemoptysis.

Where do the vast majority of pulmonary emboli originate?

Deep vein thrombosis (DVT) in the deep veins of the lower extremities.

How does a massive pulmonary embolism impair right ventricular heart function?

Increases right ventricular outflow resistance, causing acute right heart strain.

Which clinical symptom presentation should immediately raise suspicion for a pulmonary embolism?

Sudden-onset dyspnea, sharp pleuritic chest pain.

What is the key early warning symptom of laryngeal cancer?

Persistent hoarseness or voice changes lasting longer than two weeks.

Why is small cell lung carcinoma (SCLC) considered particularly aggressive?

It arises from neuroendocrine tissue, grows rapidly, and is linked to heavy smoking.

Why is lung cancer often diagnosed late in long-term smokers?

Early symptoms mimic baseline COPD or 'smoker's cough.'

How do exhalation findings clinically distinguish obstructive from restrictive pulmonary disease?

Obstructive diseases display prolonged expiration; restrictive diseases display reduced chest expansion.

What does rising PaCO2 in a patient with respiratory distress indicate?

Respiratory muscle fatigue and impending hypercapnic respiratory arrest.