COMPARISON OF PEAK OXYGEN-CONSUMPTION DURING CYCLE AND TREADMILL EXERCISE IN SEVERE CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

Background- In normal subjects treadmill exercise usually produces the greatest maximal oxygen consumption (VO(2)max). This may not bet true for patients with severe chronic obstructive pulmonary disease (COPD) in whom bicycle exercise, which offers support for the shoulder girdl e, may produce a higher oxygen consumption than treadmill exercise. Th e aim of this study was to determine which mode of exercise produced t he greatest oxygen consumption in patients with severe COPD. Methods - Eight patients with severe COPD (forced expiratory volume in one seco nd (FEV(1)) more than three standardised residuals below predicted) ex ercised to a symptom limited maximum on a bicycle and on a treadmill o n separate days. The workload on the bicycle was increased by 10 watts each minute, and the treadmill gradient was increased by 2.5% alterna te minutes whilst the speed remained constant. Measurements of oxygen consumption (VO2), ventilation (VE), heart rate, and oxygen saturation were made, and capillary blood gases were measured before and immedia tely after exercise. Lactate concentration was measured before and fou r minutes after exercise. Results - There were no differences at peak exercise be tween the two forms of exercise for VO2 (median 11.7 and 1 2.2 ml/min/kg for bicycle and treadmill, respectively), for VE (median 26.6 and 25.0 1/min, respectively). and for heart rate (median 119 an d ll5 beats/min, respectively). The median lactate levels after bicycl e exercise were higher than those after the treadmill (2.42 v 0.94 mmo l/l). Conclusions - Although only a small number of patients was studi ed and individual variability was large, there was no clear difference between the two forms of exercise. Regular bicycle exercise was unfam iliar to this group of patients and generated the greatest lactate res ponse. The results do not support the hypothesis that bicycle exercise will produce a better performance in patients with severe COPD, but t he two modes of exercise cannot be used interchangeably.