Internal Medicine · Year 3 · from Internal Medicine

Case 3: New Diagnosis of Asthma vs. COPD

Patient Presentation

A 55-year-old woman presents with 2 years of progressively worsening shortness of breath and cough. She has a 20-pack-year smoking history but quit 5 years ago. She notes symptoms are worse in the spring and when she exercises. She has a history of allergic rhinitis and eczema as a child.

Vital Signs

  • Blood Pressure: 128/78 mmHg
  • Heart Rate: 76 bpm
  • Respiratory Rate: 16/min
  • Oxygen Saturation: 97% on room air

Physical Examination

  • General: Well-appearing, no distress at rest
  • HEENT: Boggy nasal mucosa
  • Cardiovascular: Regular rate and rhythm
  • Pulmonary: Mild expiratory wheezes bilaterally, no prolonged expiration

Pulmonary Function Tests

  • Pre-bronchodilator: FEV1 68% predicted, FVC 85% predicted, FEV1/FVC 0.62
  • Post-bronchodilator: FEV1 82% predicted (improvement of 14% and 280 mL)
  • DLCO: 92% predicted (normal)

Additional Testing

  • CBC: WBC 8,500/μL with 8% eosinophils
  • Total IgE: 285 IU/mL (elevated)
  • Chest X-ray: No hyperinflation, clear lung fields

Clinical Image

Figure 3: Flow-volume loop demonstrating obstructive pattern with significant bronchodilator response (dashed line = post-bronchodilator), favoring asthma over COPD.

Image Source: Educational illustration for teaching purposes.

Questions

  1. What features favor asthma over COPD in this patient?
  • A) Smoking history
  • B) Age of onset
  • C) Significant bronchodilator response (>12% and >200 mL), atopic history, peripheral eosinophilia, normal DLCO
  • D) Chronic cough
  1. What spirometry finding defines obstructive lung disease?
  • A) FEV1 <80% predicted
  • B) FEV1/FVC ratio <0.70
  • C) FVC <80% predicted
  • D) DLCO <80% predicted
  1. What is Asthma-COPD Overlap (ACO)?
  • A) Misdiagnosis of asthma
  • B) Patients with features of both asthma and COPD, often with significant smoking history and eosinophilic inflammation
  • C) Severe asthma only
  • D) COPD with frequent exacerbations
  1. What treatment approach would be appropriate for this patient?
  1. How does DLCO help differentiate asthma from COPD?

Answers

  1. C) Significant bronchodilator response (>12% and >200 mL), atopic history, peripheral eosinophilia, normal DLCO - These features suggest asthma: reversibility >12% and >200 mL, personal/family history of atopy (allergic rhinitis, eczema), elevated eosinophils, elevated IgE, and normal DLCO (preserved gas exchange).
  1. B) FEV1/FVC ratio <0.70 - Obstructive lung disease is defined by FEV1/FVC <0.70 (or below lower limit of normal). FEV1% predicted indicates severity once obstruction is established.
  1. B) Patients with features of both asthma and COPD, often with significant smoking history and eosinophilic inflammation - ACO includes patients with persistent airflow limitation who have features of both conditions. They often have smoking history, late-onset symptoms, but also reversibility, eosinophilia, and atopy.
  1. Treatment approach:
  • Given features of both asthma and possible ACO:
  • First-line: ICS-LABA combination (e.g., fluticasone-salmeterol or budesonide-formoterol)
  • Add LAMA (tiotropium) if inadequate control
  • Avoid LABA monotherapy - always use with ICS in asthma
  • Rescue: SABA PRN or ICS-formoterol as needed
  • Allergen avoidance: Given atopic history
  • Consider: Allergy testing, evaluation for biologic therapy if eosinophilic
  1. DLCO in asthma vs. COPD:
  • Asthma: DLCO is typically normal because there is no parenchymal destruction
  • COPD (emphysema): DLCO is reduced due to alveolar destruction and loss of gas-exchanging surface area
  • Chronic bronchitis (COPD without emphysema): DLCO may be preserved
  • Normal DLCO in this patient with reversible obstruction favors asthma

Learning Points

  1. COPD exacerbations are characterized by increased dyspnea, sputum volume, and sputum purulence; treatment includes bronchodilators, steroids, antibiotics if indicated, and NIPPV for respiratory acidosis.
  1. Target SpO2 of 88-92% in COPD prevents oxygen-induced hypercapnia in chronic CO2 retainers.
  1. Severe asthma with normal/rising PCO2, silent chest, or inability to speak indicates impending respiratory failure requiring aggressive treatment.
  1. Bronchodilator reversibility (>12% and >200 mL) favors asthma; DLCO reduction suggests emphysema.
  1. ICS-LABA is first-line for asthma and ACO; LABA monotherapy is contraindicated in asthma due to increased mortality risk.

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