Asthma

• Definition: Chronic inflammatory disorder of the airways with reversible airflow obstruction and bronchial hyperresponsiveness.
• Typical presentation: Episodic wheeze, cough, dyspnea, chest tightness, often worse at night or early morning.
• Common triggers: Allergens, viral URIs, exercise, cold air, smoke, occupational exposures.

Pathophysiology

• Inflammation: Th2-mediated → ↑ IL-4 (IgE), IL-5 (eosinophils), IL-13 (mucus).
• Bronchospasm: Smooth muscle constriction.
• Mucus plugging: Goblet cell hyperplasia.
• Key reversible feature: Airway narrowing improves with bronchodilators.

Diagnosis

• Spirometry:
  • Obstruction: ↓ FEV₁/FVC (< 0.70).
  • Reversibility: ↑ FEV₁ by ≥ 12% and ≥ 200 mL after SABA.
• Peak flow monitoring: Useful for self-management.
• Methacholine challenge: For suspected asthma with normal spirometry.
• Allergy testing: Identifies triggers.

Severity Classification

(Initial Therapy)

Stepwise Management (GINA/NHLBI)

Goal: Control symptoms + prevent exacerbations.

Intermittent

• PRN low-dose ICS-formoterol or SABA alone (US guidelines still allow SABA monotherapy here).

Mild persistent

• Daily low-dose ICS (budesonide, fluticasone)
  or PRN low-dose ICS-formoterol.

Moderate persistent

• Low-dose ICS + LABA
  or medium-dose ICS.

Severe persistent

• Medium/high-dose ICS + LABA
  Consider add-on tiotropium (LAMA).

Severe persistent

• High-dose ICS + LABA
  • biologics (omalizumab, mepolizumab, dupilumab) for allergic/eosinophilic phenotypes.

Acute Exacerbation Management

Mild to moderate:

• O₂ to keep SpO₂ > 90% (> 95% in pregnancy, peds).
• Inhaled SABA (albuterol) ± SAMA (ipratropium).
• Oral steroids (prednisone 40-60 mg × 5-7 days).

Severe/life-threatening:

• Continuous nebulized SABA.
• IV steroids.
• Consider magnesium sulfate IV for bronchospasm.
• If “silent chest” (no wheezing, poor air entry) + fatigue → prepare for possible intubation.

Exam & Ward Pearls

• Asthma vs. COPD: Asthma is reversible, COPD is not.
• Nocturnal symptoms = poor control → step up therapy.
• Overuse of SABA (>2 days/week) is a red flag for poor control.
• Aspirin-exacerbated respiratory disease: asthma + nasal polyps + NSAID sensitivity → avoid NSAIDs.
• Peak flow < 50% predicted = severe exacerbation.

Quick Rescue Table