Pulmonary function abnormalities in interstitial lung disease include all of the following except –
**Core Concept**
Interstitial lung disease (ILD) is a group of disorders characterized by inflammation and scarring in the lung interstitium, leading to impaired gas exchange and pulmonary function abnormalities. The pathophysiology involves damage to the alveolar-capillary membrane, resulting in reduced lung compliance, increased resistance, and impaired diffusion capacity.
**Why the Correct Answer is Right**
The pulmonary function abnormalities in ILD typically include restrictive lung disease, characterized by reduced lung volumes (e.g., FVC, TLC) and capacities (e.g., DLCO). This is due to the scarring and inflammation in the lung interstitium, which limits lung expansion and gas exchange. Additionally, patients with ILD often exhibit impaired diffusion capacity (DLCO) due to the damage to the alveolar-capillary membrane.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because obstructive lung disease (e.g., COPD, asthma) is typically characterized by airway obstruction, increased resistance, and impaired expiratory flow rates, which is not a hallmark of ILD.
**Option B:** This option is incorrect because bronchiectasis is a condition characterized by irreversible dilation of the bronchi, often due to chronic infection or inflammation, which is not a feature of ILD.
**Option C:** This option is incorrect because pulmonary embolism is a condition characterized by a blockage of an artery in the lung, which can lead to acute respiratory distress and impaired gas exchange, but is not a hallmark of ILD.
**Clinical Pearl / High-Yield Fact**
A key feature of ILD is the presence of a restrictive pattern on pulmonary function testing, which is often accompanied by impaired diffusion capacity (DLCO). This can be remembered using the mnemonic "Restrictive Lung Disease: Reduced Lung Volumes and Capacities".
**Correct Answer:** D