Pulmonary function testing in interstitial lung diseases.

Interstitial lung diseases (ILDs) are functionally characterized by a restrictive ventilatory defect due to a reduced distensibility of the lung parenchyma. ILD patients also show a reduced exercise tolerance, the main factors limiting exercise capacity being ventilatory and gas exchange abnormalities. Functional abnormalities in ILDs are typical, but not specific. Despite the fact that different lung function patterns have been described among ILDs, they overlap and their practical application to differentiate ILDs is poor. Resting pulmonary function and exercise-induced hypoxemia can aid in defining the prognosis of ILDs and in referring patients for lung transplantation. Additionally, spirometry and diffusing capacity are useful to monitor the response of patients to therapy.