Moser C, Tirakitsoontorn P, Nussbaum E, Newcomb R, Cooper D M
Department of Pediatrics, University of California Irvine Medical Center, Irvine, CA, USA.
Am J Respir Crit Care Med. 2000 Nov;162(5):1823-7. doi: 10.1164/ajrccm.162.5.2003057.
The mechanism responsible for diminished exercise performance in cystic fibrosis (CF) is not clear. We hypothesized that reduced muscle size, rather than an intrinsic muscle defect, was the primary factor in such diminished exercise performance. Twenty-two subjects with CF (14 females and eight males, aged 6.5 to 17.7 yr, with FEV(1) of 46% to 111% predicted) participated in a study of this hypothesis, and were compared with healthy children tested in the same laboratory. Muscle size was estimated from midthigh muscle cross-sectional area (CSA) obtained by magnetic resonance imaging, and fitness was determined by progressive cycle ergometer exercise testing with breath-by-breath measurements of gas exchange. Peak oxygen consumption (V O(2)) was reduced in CF subjects (956 +/- 81 [mean +/- SEM] ml/min, as compared with 1,473 +/- 54 ml/min in controls; p < 0.00001). Surprisingly, CF subjects had a lower peak V O(2) per CSA (mean for CF subjects 70 +/- 3% predicted, p < 0.0001) than did controls, whereas muscle CSA in CF subjects was not significantly smaller than in controls. The scaling parameters of peak V O(2) and muscle CSA did not differ significantly between healthy controls (0.80 +/- 0.16) and CF subjects (1.03 +/- 0.12). Indexes of aerobic function that are less effort-dependent than peak V O(2) were also lower in the CF subjects (e.g., the slope of V O(2) versus work rate [WR] (DeltaV O(2)/DeltaWR) was 68 +/- 2% predicted; p < 0.005). The study data did not support the initial hypothesis, and suggest a muscle-related abnormality in oxygen metabolism in patients with CF.
囊性纤维化（CF）患者运动能力下降的机制尚不清楚。我们推测，肌肉大小减小而非内在肌肉缺陷是导致此类运动能力下降的主要因素。22名CF受试者（14名女性和8名男性，年龄6.5至17.7岁，FEV(1)为预测值的46%至111%）参与了这一假说的研究，并与在同一实验室测试的健康儿童进行比较。通过磁共振成像获得大腿中部肌肉横截面积（CSA）来估计肌肉大小，并通过渐进式自行车测力计运动测试并逐次呼吸测量气体交换来确定体能。CF受试者的峰值耗氧量（V O(2)）降低（956±81[平均值±标准误]ml/分钟，而对照组为1473±54 ml/分钟；p<0.00001）。令人惊讶的是，CF受试者每CSA的峰值V O(2)低于对照组（CF受试者平均值为预测值的70±3%，p<0.0001），而CF受试者的肌肉CSA并不显著小于对照组。健康对照组（0.80±0.16）和CF受试者（1.03±0.12）之间，峰值V O(2)和肌肉CSA的缩放参数无显著差异。CF受试者中，比峰值V O(2)依赖努力程度更低的有氧功能指标也较低（例如，V O(2)与工作率[WR]的斜率[DeltaV O(2)/DeltaWR]为预测值的68±2%；p<0.005）。研究数据不支持最初的假说，并提示CF患者存在与肌肉相关的氧代谢异常。
