title: Effect of mild-to-moderate airflow limitation on exercise capacity.
abstract: To determine the effect of mild-to-moderate airflow limitation on exercise tolerance and end-expiratory lung volume (EELV), we studied 9 control subjects with normal pulmonary function [forced expired volume in 1 s (FEV1) 105% pred; % of forced vital capacity expired in 1 s (FEV1/FVC%) 81] and 12 patients with mild-to-moderate airflow limitation (FEV1 72% pred; FEV1/FVC % 58) during progressive cycle ergometry. Maximal exercise capacity was reduced in patients [69% of pred maximal O2 uptake (VO2max)] compared with controls (104% pred VO2max, P less than 0.01); however, maximal expired minute ventilation-to-maximum voluntary ventilation ratio and maximal heart rate were not significantly different between controls and patients. Overall, there was a close relationship between VO2max and FEV1 (r2 = 0.62). Resting EELV was similar between controls and patients [53% of total lung capacity (TLC)], but at maximal exercise the controls decreased EELV to 45% of TLC (P less than 0.01), whereas the patients increased EELV to 58% of TLC (P less than 0.05). Overall, EELV was significantly correlated to both VO2max (r = -0.71, P less than 0.001) and FEV1 (r = -0.68, P less than 0.001). This relationship suggests a ventilatory influence on exercise capacity; however, the increased EELV and associated pleural pressures could influence cardiovascular function during exercise. We suggest that the increase in EELV should be considered a response reflective of the effect of airflow limitation on the ventilatory response to exercise.
authors.affiliation: Methodist Hospital, Baylor College of Medicine, Houston, Texas 77030.
authors.forename: T G
authors.initials: TG
authors.lastname: Babb
authors.forename: R
authors.initials: R
authors.lastname: Viggiano
authors.forename: B
authors.initials: B
authors.lastname: Hurley
authors.forename: B
authors.initials: B
authors.lastname: Staats
authors.forename: J R
authors.initials: JR
authors.lastname: Rodarte
mesh_terms: D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000503:physiopathology*; D008176:Lung Volume Measurements; D008297:Male; D008451:Maximal Voluntary Ventilation / Q000502:physiology; D008875:Middle Aged; D010101:Oxygen Consumption; D015656:Respiratory Mechanics / Q000502:physiology