Cardiopulmonary exercise testing in interstitial lung disease

Interstitial lung disease (ILD) can determine severe lung function impairment both at rest and during exercise. Usually, resting measurements of lung and cardiac function give enough information on the degree of the disease. Thus, exercise testing should be reserved only for particular situations such as presence at the same time of cardiac and respiratory involvement, symptomatic patients with normal spirometry, and to check the response to therapy. A better understanding of the pathophysiology and cardiorespiratory consequences of ILD can give an important contribution in improving methods of exercise testing to assess disability. In this perspective, we analyze the factors limiting exercise performance: the progressive hypoxemia that appears or is worsened by exertion; the ventilatory abnormalities that lead to a rapid shallow breathing pattern with a V̇E that reach the MVV; and the cardiovascular limitation with low maximum heart rate, low cardiac output and high PVR and PAP.