A 58-year-old man with a 40 pack-year smoking history presents with progressive dyspnea on exertion and chronic cough productive of scanty sputum. On examination, he has diminished breath sounds bilaterally and prolonged expiration. Spirometry shows FEV₁ = 52% predicted, FVC = 78% predicted, and FEV₁/FVC ratio = 0.58. His DLCO is 65% predicted. What is the most likely diagnosis based on these spirometric findings?

Explanation

## Spirometric Pattern Analysis **Key Point:** The FEV₁/FVC ratio <0.70 (here 0.58) is the hallmark of obstructive airway disease, confirming airflow obstruction. ### Pattern Recognition | Parameter | Patient Value | Expected (Normal) | Interpretation | |-----------|---------------|-------------------|----------------| | FEV₁ | 52% predicted | >80% | Moderately reduced | | FVC | 78% predicted | >80% | Mildly reduced | | FEV₁/FVC | 0.58 | >0.70 | **Obstructive pattern** | | DLCO | 65% predicted | >80% | Reduced (emphysema) | **High-Yield:** In obstructive disease, FEV₁ falls disproportionately more than FVC, driving the ratio below 0.70. The reduced DLCO in the context of smoking history and emphysematous features (prolonged expiration, diminished breath sounds) confirms emphysema as the underlying pathology. ### Clinical Correlation **Clinical Pearl:** Emphysema causes alveolar destruction and loss of elastic recoil, leading to: - Early airway collapse during expiration (air trapping) - Reduced DLCO (loss of alveolar surface area) - Prolonged expiratory time This patient's smoking history, clinical presentation (dyspnea, cough), and spirometric-DLCO profile are classic for COPD with emphysema. **Mnemonic — Obstructive vs Restrictive:** **FORD** - **F**EV₁/FVC ratio: **O**bstructive <0.70, **R**estrictive >0.70 - **O**bstructive: FEV₁ ↓↓, FVC ↓ (or normal) - **R**estrictive: FEV₁ ↓, FVC ↓↓ (proportional) - **D**LCO: **O**bstructive (emphysema) ↓, **R**estrictive (ILD) variable [cite:Harrison 21e Ch 246]