A 68-year-old woman with idiopathic pulmonary fibrosis undergoes spirometry. Her results show FEV₁ 70% predicted, FVC 65% predicted, FEV₁/FVC ratio 0.82, TLC 60% predicted, and normal inspiratory and expiratory flow curves. Which of the following is NOT a characteristic feature of the restrictive pattern seen in this patient?

Explanation

## Restrictive Pattern on Spirometry **Key Point:** A restrictive pattern is characterized by **proportional reduction** in both FEV₁ and FVC, resulting in a **preserved or elevated FEV₁/FVC ratio** (≥0.70). The defining feature is **reduced TLC**. ### Hallmark Features of Restriction | Feature | Finding | Mechanism | |---------|---------|----------| | FEV₁ | **Decreased** (proportionally) | Reduced lung volume | | FVC | **Decreased** (proportionally) | Reduced lung volume | | FEV₁/FVC | **Normal or elevated** (≥0.70) | Proportional reduction | | TLC | **Decreased** (<80% predicted) | Defining criterion | | RV | **Decreased** | Loss of lung volume | | Inspiratory curve | **Normal or steep** | No obstruction | | Expiratory curve | **Normal (not scooped)** | No flow limitation | | PEF | **Normal or slightly reduced** | No dynamic airway collapse | **High-Yield:** In restriction, the **flow rates are preserved relative to lung volume**; the expiratory curve remains **linear or convex**, NOT scooped. ### Why Option 3 is Wrong A **scooped-out (concave) expiratory curve** is a hallmark of **obstruction**, not restriction. In obstruction, dynamic airway collapse during forced expiration causes the characteristic concave shape. In restriction, the expiratory curve is **normal (linear or convex)** because there is no flow limitation—only reduced volume. Decreased PEF in isolation *can* occur in restriction (due to reduced lung volume), but a **scooped curve is pathognomonic for obstruction** and is **NOT** seen in pure restrictive disease. ### Why Options 1, 2, 4 Are Correct - **Option 1 (Proportional reduction, preserved ratio):** Defining feature of restriction. Both FEV₁ and FVC fall together, maintaining the ratio ≥0.70. - **Option 2 (Decreased TLC and RV):** Loss of lung volume is the hallmark of restriction; both static lung volumes are reduced. - **Option 4 (Reduced VC, normal/increased inspiratory flow):** Vital capacity is reduced, but inspiratory flow rates are preserved because there is no obstruction to inhalation. **Clinical Pearl:** In idiopathic pulmonary fibrosis (IPF), the restrictive pattern is accompanied by reduced DLCO (due to fibrotic remodeling). The combination of restriction + low DLCO is highly suggestive of interstitial lung disease. **Mnemonic — RESTRICTION vs. OBSTRUCTION:** - **R**estriction: **R**atio preserved, **R**V low, **R**ound (normal) curve - **O**bstruction: **O**bviously low ratio, **O**ver-inflated (high RV), **O**utward (scooped) curve [cite:West Respiratory Physiology 10e Ch 9; Harrison 21e Ch 297]