A 52-year-old man with chronic obstructive pulmonary disease (COPD) undergoes spirometry. All of the following findings are consistent with COPD EXCEPT:

Explanation

## Spirometric Findings in COPD **Key Point:** COPD is characterized by airflow obstruction, air trapping, and hyperinflation. TLC is typically **increased** (not decreased) in COPD due to loss of elastic recoil and air trapping, not decreased. ### Classic Spirometric Pattern in COPD ```mermaid flowchart TD A[COPD Pathophysiology]:::outcome --> B[Loss of elastic recoil<br/>Air trapping<br/>Emphysematous destruction]:::outcome B --> C[Airflow obstruction]:::outcome C --> D[FEV₁/FVC < 0.70]:::outcome B --> E[Hyperinflation]:::outcome E --> F[Increased RV]:::outcome E --> G[Increased FRC]:::outcome E --> H[Increased TLC]:::outcome F --> I[RV/TLC > 0.40]:::outcome ``` ### Comparison of Lung Volumes in COPD vs. Restrictive Disease | Parameter | COPD (Obstructive) | Restrictive Disease | | --- | --- | --- | | FEV₁/FVC | **Decreased** (< 0.70) | Normal or increased | | TLC | **Increased** (hyperinflation) | **Decreased** | | RV | **Increased** (air trapping) | Normal or decreased | | FRC | **Increased** | Decreased | | RV/TLC | **Increased** (> 0.40) | Normal | | VC | Decreased | Decreased | **High-Yield:** In COPD, the hallmark is **hyperinflation** — increased TLC, RV, and FRC. In restrictive disease, all volumes are reduced. Do not confuse the two. ### Why Option 3 Is Wrong Option 3 states: "Decreased total lung capacity (TLC) secondary to emphysematous destruction of alveolar walls." This is **incorrect**. Although emphysematous destruction does occur in COPD, it leads to **loss of elastic recoil and air trapping**, which causes **hyperinflation and increased TLC**, not decreased TLC. Decreased TLC is seen in **restrictive** diseases (pulmonary fibrosis, pneumoconiosis, chest wall restriction), not COPD. **Clinical Pearl:** A patient with COPD who has a decreased TLC should prompt investigation for a concurrent restrictive process (e.g., pulmonary fibrosis superimposed on emphysema, or asbestos-related disease). **Mnemonic:** **COPD = Hyperinflation** (↑TLC, ↑RV, ↑FRC); **Restrictive = Reduction** (↓TLC, ↓VC, ↓RV). [cite:Harrison Principles of Internal Medicine 21e Ch 298]