• Obstructive airway diseases (↑ resistance to airflow):
  • Asthma
  • Chronic obstructive pulmonary disease (COPD)
  • Bronchitis
  • Bronchiectasis
  • Cystic fibrosis
  • Emphysema
  • Tumor
  • Foreign body
  • Vocal cord dysfunction,
  • Anaphylaxis
• Restrictive lung diseases:
  • Interstitial lung diseases (e.g., pulmonary fibrosis, sarcoidosis)
  • Obesity hypoventilation syndrome
• Infections:
  • Pneumonia
  • Tuberculosis
• Pulmonary vascular diseases:
  • Pulmonary embolism
  • Pulmonary hypertension
  • Tumor emboli
  • Pulmonary artery vasculitis
• Pleural diseases:
  • Pleural effusion
  • Pneumothorax
  • Pleural fibrosis
• Other:
  • Acute respiratory distress syndrome (ARDS)
  • Foreign body aspiration
  • Pulmonary edema: cardiogenic or noncardiogenic
  • Atelectasis

• 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.

• Anemia
• Carbon monoxide poisoning
• Methemoglobinemia

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

• Anxiety or panic disorders
• Hyperventilation syndrome

6.

• Diabetic ketoacidosis
• Lactic acidosis
• Hypothyroidism or hyperthyroidism

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

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