Pathophysiologic Mechanisms

To evaluate the frequency ofthe causes ofexercise limitation in patients with chronic pulmonary disease and to assess the relationship between the resting pulmonary functional parameters and the degree of exercise dyspnea, we reviewed the data from 88 consecutive stable patients with chronic lung disease (62 COPD, 16 interstitial lung disease [ILD]). In each patient, the intensity of dyspnea was measured by a Borg scale (BS) during an incremental symptom-limited exercise test. COPD patients stopped exercise due to fatigue (46%), dyspnea (36%), cardiac limitation (12%), and peripheral circulatory limitation (6%). liD patients stopped exercise due to dyspnea (62%), fatigue (2.5%), and cardiac limitation (12%). In all patients, dyspnea severity increased linearly with exercise intensity as measured as Vo5, VE, and VE/MVV. The severity of dyspnea expressed as the slope of the relationship between BS and VEIMVV (DBS/D[VE/MVV]) showed in COPD a significant inverse correlation with VC, FEy1, MIP, and a positive