Comprehensive Medical Lecture Note Dyspnea (Shortness of Breath)

 

Comprehensive Medical Lecture Note

Dyspnea (Shortness of Breath)

Definition:

Dyspnea is the subjective experience of breathing discomfort that consists of qualitatively distinct sensations that vary in intensity. It is often described by patients as "shortness of breath," "tightness in the chest," or "difficulty breathing."

Clinical Relevance:

Dyspnea is a common symptom encountered in clinical practice and may be a sign of underlying cardiopulmonary, neuromuscular, metabolic, or psychogenic disorders. It is a key symptom requiring thorough evaluation and timely management to reduce morbidity and mortality.

Major Classifications of Dyspnea

• Acute Dyspnea: Duration <72 hours. Usually life-threatening. Causes include pulmonary embolism, acute asthma, pneumothorax, pneumonia, myocardial infarction, or anaphylaxis.
• Chronic Dyspnea: Duration >1 month. Often caused by COPD, interstitial lung disease, heart failure, obesity, or deconditioning.
• Exertional Dyspnea: Breathlessness during physical activity. Common in cardiac and respiratory diseases.
• Orthopnea: Difficulty breathing while lying flat. Classic in congestive heart failure.
• Paroxysmal Nocturnal Dyspnea (PND): Sudden breathlessness during sleep, typically due to heart failure.
• Trepopnea: Dyspnea occurring in a specific lateral decubitus position (seen in unilateral lung disease or heart disease).
• Platypnea: Dyspnea when sitting or standing upright, relieved by lying down (seen in hepatopulmonary syndrome).

Pathophysiology

Dyspnea arises due to mismatch between respiratory drive and the ability of the respiratory system to respond. The primary mechanisms include:

• Increased ventilatory demand (e.g., hypoxia, hypercapnia)
• Impaired ventilatory mechanics (e.g., obstruction, stiffness)
• Altered central perception of breathing
• Neuromuscular limitations in respiratory muscles

Etiological Classification (Mnemonic: CARDIAC-P)

• Cardiac: Heart failure, myocardial infarction, arrhythmias, pericardial effusion
• Asthma and COPD: Chronic bronchitis, emphysema
• Respiratory infections: Pneumonia, bronchitis, tuberculosis
• Deep vein thrombosis / Pulmonary embolism
• Interstitial lung diseases: Idiopathic pulmonary fibrosis, sarcoidosis
• Anemia or metabolic: Acidosis, sepsis, fever, anemia
• Central causes: Anxiety, panic attacks, brainstem lesions
• Pneumothorax, pleural effusion

History and Physical Examination

History Focus:

• Onset: Sudden (PE, MI) vs. gradual (CHF, ILD)
• Duration and progression
• Associated symptoms: chest pain, cough, wheeze, fever, hemoptysis, weight loss
• Triggers and relieving factors
• Past medical history: asthma, COPD, cardiac conditions, smoking
• Medication and allergy history

Physical Exam:

• General: Respiratory distress, accessory muscle use, cyanosis
• Vitals: RR, HR, BP, temperature, O₂ saturation
• Lung: Wheeze, crackles, decreased breath sounds, dullness to percussion
• Heart: S3 gallop, murmurs, elevated JVP
• Extremities: Edema, DVT signs

Investigations

• Basic labs: CBC, BNP, D-dimer, ABG, electrolytes, LFTs, renal profile
• ECG: Evaluate for ischemia, arrhythmia
• CXR: Pneumonia, pneumothorax, CHF, pleural effusion
• Pulse oximetry and arterial blood gas (ABG)
• Echocardiogram: Evaluate for cardiac function and pericardial disease
• CT Pulmonary Angiography: Gold standard for PE diagnosis
• PFTs: For chronic dyspnea and obstructive/restrictive diseases
• COVID-19 test: If clinically suspected

Management

• Address underlying cause (infection, heart failure, embolism, obstruction, anemia)
• Oxygen therapy if hypoxic (keep SpO₂ > 92%)
• Bronchodilators for obstructive airway disease (e.g., salbutamol, ipratropium)
• Diuretics in congestive heart failure
• Antibiotics if pneumonia suspected
• Anticoagulation for pulmonary embolism
• Psychological support in anxiety-related dyspnea

Red Flag Signs

• Sudden severe dyspnea with chest pain (suspect PE, MI)
• Stridor or signs of airway obstruction
• Altered mental status or hypoxia unresponsive to oxygen
• Hemodynamic instability (hypotension, tachycardia)
• Use of accessory muscles and fatigue

Prognosis

The prognosis depends entirely on the underlying cause and promptness of intervention. Chronic causes need long-term multidisciplinary care and follow-up.

References and Resources

• Harrison's Principles of Internal Medicine, 21st Edition
• Goldman-Cecil Medicine, 26th Edition
• Davidson’s Principles and Practice of Medicine
• National Heart, Lung, and Blood Institute (NHLBI)
• GOLD and GINA Guidelines for COPD and Asthma

This lecture is for medical educational purposes only. Always correlate clinically and consult standard guidelines and specialists when managing patients.