VENTILATORY RESPONSE TO POSITIVE AND NEGATIVE WORK IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

In healthy subjects, oxygen consumption and cardiorespiratory response s are lower during eccentric exercise (negative work, W-neg) than duri ng concentric exercises (positive work, W-pos) at the same work load. The aim of the present study was to investigate the ventilatory respon se to W-neg in patients with chronic obstructive pulmonary disease (CO PD). The study population consisted of 12 subjects with COPD [forced e xpiratory volume in 1 s (FEV(1)) mean (so): 1.5 (0.4)1, 46 (16)% of pr edicted]. Concentric and eccentric exercise tests (6 min exercise; int erval greater than or equal to 1 h) were performed in random order at constant work loads of 25 and 50% of the individual maximal (positive) work capacity. Expired ventilation per minute (VE), oxygen consumptio n (VO2) and carbon dioxide production (VCO2) were 30% lower during W-n eg than during W-pos for both work intensities. The breathing reserve during 25%W-neg was 11 (8)% and during 50%W-neg was 18 (14)% higher th an during W-pos at corresponding work loads (P<0.01). VE/VO2 and VE/VC O2 were similar during W-pos and W-neg. Arterial carbon dioxide tensio n (PaCO2) increased by 0.1 (0.4) kPa during 50%W-neg and by 0.7 (0.5) kPa during 50%W-pos (P<0.01). During 50%W-neg, perceived leg effort (m odified Borg scale) tended to be higher than perceived breathlessness (2.4 (1.2) vs. 2.0 (1.1). It was concluded that in subjects with COPD, the ventilatory requirements of W-neg were considerably lower than th ose of W-pos at similar work loads up the 50% of maximal work capacity . During W-neg, the ventilatory reserve was higher and gas exchange wa s less disturbed as a result of a lower VO2 and VCO2.