Troutman W B, Barstow T J, Galindo A J, Cooper D M
Department of Pediatrics, School of Medicine, University of California Los Angeles, Westwood, USA.
J Am Coll Cardiol. 1998 Mar 1;31(3):668-73. doi: 10.1016/s0735-1097(97)00545-7.
Novel protocols were used to focus on dynamic cardiorespiratory function during submaximal exercise and on the recovery from 1-min pulses of exercise in children who had undergone Fontan corrections for single-ventricle lesions.
Particularly in children, maximal oxygen uptake (VO2max), which is commonly used to assess the functional capability of patients after the Fontan procedure, is highly effort dependent and not physiologic and leads to uncomfortable metabolic and cardiorespiratory stress. Alternative approaches include the measurement of dynamic responses during progressive exercise and recovery after short bursts of exercise. These strategies yield mechanistic insight into cardiorespiratory impairment and can be used to gauge limitations in daily life activity.
Sixteen patients (mean [+/-SD] age 12.2 +/- 2.4 years; 9 boys) and 10 age-matched control subjects (mean age 12.2 +/- 2.4 years; 6 boys) performed two separate cycle ergometer tests in which gas exchange was measured on a breath by breath basis: 1) Progressive exercise was used to determine the dynamic relation among VO2, carbon dioxide production (VCO2), ventilation (VE), heart rate (HR) and work rate (WR). 2) A 1-min constant WR test was used to determine the recovery time for gas exchange and HR.
Peak VO2 and anaerobic threshold were reduced in patients who underwent the Fontan procedure compared with control subjects by 57% and 52%, respectively (p < 0.001). Dynamic relations during progressive exercise--deltaVO2/deltaHR and deltaVO2/deltaWR--were decreased (p < 0.001) and deltaVE/deltaVCO2 was increased (p < 0.005) in the Fontan group patients. Recovery times for HR and VO2 were prolonged in the Fontan group patients by 154% and 69%, respectively (p < 0.01).
The results demonstrate that submaximal gas exchange responses to progressive exercise and recovery times after brief high intensity exercise are abnormal in patients after the Fontan procedure. These observations complement the findings of reduced VO2max observed here and by others. We speculate that the mechanisms for these responses are related to 1) a pervasive reduction in stroke volume for both low and high intensity exercise, 2) an abnormal linkage of ventilation to tissue carbon dioxide production, and 3) increased dependence on anaerobic metabolism in skeletal muscles. The prolonged recovery of HR and VO2 provides a possible mechanism for reduced physical activity.
采用新方案聚焦于接受单心室病变Fontan矫治术的儿童在次极量运动期间的动态心肺功能以及运动1分钟脉冲后的恢复情况。
特别是在儿童中，常用于评估Fontan手术后患者功能能力的最大摄氧量（VO2max）高度依赖运动强度且不符合生理情况，会导致不适的代谢和心肺应激。替代方法包括测量渐进性运动期间的动态反应以及短时间运动爆发后的恢复情况。这些策略能深入了解心肺功能损害机制，并可用于评估日常生活活动中的限制。
16例患者（平均[±标准差]年龄12.2±2.4岁；9名男孩）和10名年龄匹配的对照受试者（平均年龄12.2±2.4岁；6名男孩）进行了两项单独的蹬车测力计测试，逐次呼吸测量气体交换：1）渐进性运动用于确定VO2、二氧化碳产生量（VCO2）、通气量（VE）、心率（HR）和工作率（WR）之间的动态关系。2）1分钟恒定WR测试用于确定气体交换和HR的恢复时间。
与对照受试者相比，接受Fontan手术的患者的峰值VO2和无氧阈值分别降低了57%和52%（p<0.001）。Fontan组患者在渐进性运动期间的动态关系——ΔVO2/ΔHR和ΔVO2/ΔWR——降低（p<0.001），而ΔVE/ΔVCO2增加（p<0.005）。Fontan组患者的HR和VO2恢复时间分别延长了154%和69%（p<0.01）。
结果表明，接受Fontan手术的患者在次极量运动时的气体交换反应以及短暂高强度运动后的恢复时间均异常。这些观察结果补充了此处及其他研究中观察到的VO2max降低的发现。我们推测这些反应的机制与以下因素有关：1）低强度和高强度运动时每搏输出量普遍降低；2）通气与组织二氧化碳产生之间的异常关联；3）骨骼肌对无氧代谢的依赖性增加。HR和VO2恢复时间延长为体力活动减少提供了一种可能的机制。
