Asthma Exacerbation

Pulmonology

OverviewWhoPresentationMechanismWorkupManagementPivots

Illness script · Pulmonology

Asthma Exacerbation

Acute worsening of reversible airflow obstruction from bronchospasm, mucosal edema, and mucus plugging in a known or new asthmatic.

This illness script for Asthma Exacerbation covers predisposing factors, classic presentation, mechanism, workup, management, and the clinical pivots that separate it from look-alikes—written for USMLE Step 1 and clerkship reasoning.

Updated Jul 19, 2026All scripts

01

Predisposing factors

  • Atopy triad: asthma, eczema, allergic rhinitis
  • Triggers: allergens, viral URIs (most common), exercise, cold air, NSAIDs, beta-blockers
  • Childhood onset more common; adult-onset often non-atopic
  • Obesity, smoking, GERD increase severity
  • Prior intubation or ICU admission = high-risk patient

02

Presentation

  • Wheezing, cough, chest tightness, dyspnea — often worse at night or early morning
  • Tachypnea, accessory muscle use, prolonged expiratory phase
  • Pulsus paradoxus >25 mmHg signals severe obstruction
  • Silent chest = no airflow moving — pre-arrest, immediate intervention needed
  • Symptoms reversible with bronchodilator (key feature distinguishing from fixed obstruction)

03

Pathophysiology

  • IgE-mediated (or non-IgE) mast cell degranulation → bronchospasm (early phase)
  • Late phase: eosinophilic inflammation, mucosal edema, mucus hypersecretion
  • Air trapping → dynamic hyperinflation → increased work of breathing
  • Ventilation-perfusion mismatch → hypoxemia; CO2 rises late and is ominous

04

Diagnostics

  • Peak expiratory flow (PEF) or FEV1: <40% predicted = severe exacerbation
  • Pulse oximetry: SpO2 <92% warrants aggressive treatment
  • ABG: normal or low PaCO2 early; rising PaCO2 = respiratory fatigue/failure
  • CXR: hyperinflation ± to rule out pneumonia, pneumothorax — not routine in mild cases
  • Spirometry (pre/post bronchodilator): FEV1/FVC <0.70 with ≥12% reversibility confirms asthma

05

Management

  • First-line: SABA (albuterol) via MDI or nebulizer — repeat q20 min x3
  • Add ipratropium (anticholinergic) for moderate-severe exacerbations
  • Systemic corticosteroids (oral or IV) early — reduce relapse and hospitalization
  • Supplemental O2 to maintain SpO2 ≥92%; Mg sulfate IV for severe refractory cases
  • Heliox, IV ketamine, or intubation for impending respiratory failure — avoid high tidal volumes
  • Discharge when PEF >70% predicted, SpO2 ≥92% on room air, symptoms controlled

06

Clinical pivots

How to separate this script from the look-alikes that show up on exams and on the wards.

  • COPD Exacerbation

    Age >40, smoking history, fixed (irreversible) obstruction on PFTs, no childhood atopy

  • Cardiac Asthma (Acute Pulmonary Edema)

    Crackles, S3 gallop, JVD, BNP elevated, responds to diuresis not bronchodilators

  • Vocal Cord Dysfunction

    Inspiratory stridor, normal PFTs between episodes, paradoxical cord motion on laryngoscopy

  • Foreign Body Aspiration

    Sudden onset in child, unilateral wheeze, hyperinflation on expiratory CXR

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Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.