Etiology

Dyspnea, or shortness of breath, has a wide range of potential etiologies. These can be grouped into categories based on the underlying systems involved. Here’s an organized overview:

1. Respiratory Causes

• Obstructive airway diseases:
  • Asthma
  • Chronic obstructive pulmonary disease (COPD)
  • Bronchitis
• Restrictive lung diseases:
  • Interstitial lung diseases (e.g., pulmonary fibrosis, sarcoidosis)
  • Obesity hypoventilation syndrome
• Infections:
  • Pneumonia
  • Tuberculosis
• Pulmonary vascular diseases:
  • Pulmonary embolism
  • Pulmonary hypertension
• Pleural diseases:
  • Pleural effusion
  • Pneumothorax
• Other:
  • Acute respiratory distress syndrome (ARDS)
  • Foreign body aspiration

2. Cardiac Causes

• Heart failure (left or right-sided)
• Acute coronary syndrome or myocardial infarction
• Valvular heart disease (e.g., aortic stenosis, mitral regurgitation)
• Pericardial diseases (e.g., pericarditis, cardiac tamponade)
• Arrhythmias (e.g., atrial fibrillation, tachycardia)

3. Hematologic Causes

• Anemia
• Carbon monoxide poisoning
• Methemoglobinemia

4. Neuromuscular and Structural Causes

• Neuromuscular diseases (e.g., myasthenia gravis, Guillain-Barré syndrome)
• Diaphragmatic paralysis
• Kyphoscoliosis

5. Psychogenic Causes

• Anxiety or panic disorders
• Hyperventilation syndrome

6. Metabolic and Endocrine Causes

• Diabetic ketoacidosis
• Lactic acidosis
• Hypothyroidism or hyperthyroidism

7. Miscellaneous Causes

• Obesity
• Deconditioning or physical inactivity
• Drug-induced (e.g., beta-blockers, chemotherapy agents)
• High altitude or hypoxia
• Toxic exposures (e.g., smoke inhalation, allergens)

Approach to Evaluation

• History: Assess duration (acute, subacute, chronic), associated symptoms, triggers, and past medical history.
• Physical Examination: Focus on respiratory rate, oxygen saturation, heart and lung sounds, and any evidence of systemic disease.
• Investigations: Depending on suspected etiology:
  • Chest X-ray, CT scan, or MRI
  • Pulmonary function tests
  • Blood tests (CBC, D-dimer, ABG)
  • Echocardiogram or ECG
  • V/Q scan or CT pulmonary angiography