A patient's spirometry shows FVC = 3.5 L, FEV₁ = 2.8 L, and FEV₁/FVC ratio = 80%. Which pattern does this represent?

Explanation

## Spirometric Patterns: Classification **Key Point:** The FEV₁/FVC ratio is the most important discriminator between obstructive and restrictive patterns. A normal ratio is ≥70% (or ≥75% by some guidelines). An FEV₁/FVC of 80% is clearly normal. ## Interpretation of Spirometric Parameters | Pattern | FEV₁/FVC Ratio | FVC | FEV₁ | Clinical Example | |---------|----------------|-----|------|------------------| | **Normal** | ≥70% | Normal | Normal | Healthy individual | | **Obstructive** | <70% | Normal or ↑ | ↓ | COPD, asthma | | **Restrictive** | ≥70% (preserved) | ↓ | ↓ | Pulmonary fibrosis, chest wall disease | | **Mixed** | <70% | ↓ | ↓ | Advanced COPD + fibrosis | ## Analysis of This Case 1. **FEV₁/FVC = 80%** → This is ≥70%, so the ratio is **preserved** (normal) 2. **FVC = 3.5 L** → Within normal range (predicted ~4.0–4.5 L for average adult) 3. **FEV₁ = 2.8 L** → Within normal range (predicted ~3.0–3.5 L) **High-Yield:** A preserved FEV₁/FVC ratio rules out obstructive disease. Obstructive diseases (COPD, asthma, bronchiectasis) always show FEV₁/FVC <70% because airway collapse preferentially reduces FEV₁ more than FVC. **Mnemonic: FERN** — FEV₁/FVC Elevated = Restrictive; Normal = Normal; Reduced = obstructive (Reduced ratio = Reduced airway patency) **Clinical Pearl:** In restrictive disease, both FEV₁ and FVC are reduced proportionally, so the ratio remains preserved (≥70%). In obstructive disease, FEV₁ is disproportionately reduced, causing the ratio to fall below 70%.