How can pulmonary function tests assist in evaluating interstitial lung disease?

Pulmonary function tests (PFTs) are critical in evaluating interstitial lung disease (ILD) because one of the hallmark features of ILD is a restrictive lung pattern, which is characterized by reduced lung volumes and total lung capacity. The restrictive pattern can be identified through measures such as a decreased forced vital capacity (FVC) when compared to normal ranges.

Additionally, in many cases of ILD, the diffusing capacity of the lungs for carbon monoxide (DLCO) may also be normal or decreased. A reduced DLCO indicates impaired gas exchange, which can further highlight the presence of interstitial inflammation or fibrosis that compromises the alveolar-capillary interface. Therefore, revealing a restrictive pattern with normal or decreased diffusing capacity is a clear indication of the pathological changes occurring in the lungs due to interstitial lung disease.

Other choices do not specifically address the characteristics of ILD. For example, indicating airflow obstruction is more indicative of obstructive lung diseases, such as asthma or chronic obstructive pulmonary disease (COPD). Demonstrating improved lung capacity would not generally be consistent with ILD, as these patients often exhibit decreased lung volumes. Lastly, while measuring arterial blood gas levels can provide information about oxygenation and acid-base status, it does