## Obstructive Pattern on Spirometry **Key Point:** An FEV₁/FVC ratio <0.70 with reduced FEV₁ defines airflow obstruction. The most common cause globally and in India is COPD, particularly in smokers. ### Spirometric Features of COPD - FEV₁/FVC <0.70 (hallmark of obstruction) - Reduced FEV₁ (severity correlates with disease stage) - Normal or elevated TLC (air trapping) - Increased RV (residual volume) and RV/TLC ratio ### Why COPD is Most Common | Feature | COPD | Asthma | Bronchiectasis | ILD | |---------|------|--------|-----------------|-----| | **FEV₁/FVC** | <0.70 | <0.70 | <0.70 | >0.70 (restrictive) | | **Reversibility** | Minimal | Marked (>12% improvement) | Minimal | None | | **TLC** | Normal/↑ | Normal/↑ | Normal/↑ | ↓ | | **Prevalence** | Highest in smokers | Variable | Rare | Lower | **High-Yield:** COPD is the 3rd leading cause of death worldwide and the most common cause of obstructive spirometry in a smoking population. The progressive, irreversible airflow obstruction distinguishes it from reversible asthma. **Clinical Pearl:** In this case, the smoking history, progressive dyspnea, and irreversible obstruction pattern (implied by the fixed FEV₁/FVC) point strongly to COPD rather than asthma, which typically shows bronchodilator reversibility. ### Diagnostic Criteria (GOLD 2023) - Post-bronchodilator FEV₁/FVC <0.70 confirms persistent airflow limitation - Severity graded by FEV₁ % predicted (GOLD 1–4)
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.