LUNG-VOLUME REDUCTION SURGERY IMPROVES MAXIMAL O-2 CONSUMPTION, MAXIMAL MINUTE VENTILATION, O-2 PULSE, AND DEAD SPACE-TO-TIDAL VOLUME RATIODURING LEG CYCLE ERGOMETRY

Early experience suggests that lung volume reduction surgery improves exercise tolerance as measured by the 6-min walk distance in patients with emphysema. To identify the physiologic mechanism(s) by which lung volume reduction surgery improved exercise, we performed progressive cardiopulmonary exercise testing, including rest and peak exercise blo od gas determinations, on 21 consecutive patients before and 3 mo afte r lung volume reduction surgery. Maximal work (median, range, % change ) increased 17.5 watts (-13 to +44 watts, 46%, p < 0.05), maximal oxyg en consumption increased 0.16 L/min (-0.17 to +0.48, 25%, p < 0.05), m aximal ventilation increased 6.6 L/min (-7 to +26 L/min, 27%, p < 0.05 ), and the dead space/tidal volume ratio at peak exercise decreased 0. 07 (-0.22 to +0.09, 12%, p < 0.05), exclusively as a result of an incr ease in the tidal volume. After lung volume reduction surgery heart ra te decreased at the point of isowatt exercise, from 115 to 111 beats/m in (p < 0.05). No difference was observed in the other physiologic var iables measured at isowatt exercise. In 13 patients exercised while br eathing room air, the alveolar-to-arterial O-2 difference increased, a nd the arterial O-2 tension decreased from rest to peak exercise both before and after the operation, but significant changes in this respon se were not observed after surgery. The primary problem limiting exerc ise performance in these patients was the limited ventilatory capacity as 16 and 13 of the 21 subjects developed acute respiratory acidemia at peak exercise before and after surgery, respectively. Lung volume r eduction surgery in patients with severe emphysema improved maximal ve ntilation, thereby improving maximal exercise performance.