Exercise testing in interstitial lung disease.

Studies of arterial blood gases during exercise provide the most accurate index of the pathologic severity of intersitial lung disease. For detection of early disease or assessment of treatment, resting pulmonary function tests, including single-breath carbon monoxide diffusing capacity, are adequate, although occasionally exercise studies may add unique information. Exercise studies may also be useful in assessing patients with combined cardiopulmonary disease or those whose symptoms are disproportionate to their resting pulmonary function.