Effects of respiratory muscle work on cardiac output and its distribution during maximal exercise
Effects of respiratory muscle work on cardiac output and its distribution during maximal exercise
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DOI：
10.1152/jappl.1998.85.2.609
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发表时间：
1998-08-01
影响因子：
3.3
通讯作者：
Dempsey, JA
中科院分区：
文献类型：
--
作者：
Harms, CA;Wetter, TJ;Dempsey, JA
我们最近已经证明，最大运动时呼吸功的变化会影响腿部血流量和腿部血管传导（C. A. Harms， M. A. Babcock， S. R. McClaran， D. F. Pegelow， G. A. Nickele， W. B. Nelson和J. A. Dempsey）。j:。生理学报。82:1573-1583,1997)。我们目前的研究检查了最大运动时呼吸功对心输出量（CO）变化的影响。8名男性自行车运动员[最大o -2消耗((V) / dot o(2max)): 62 +/- 5ml kg-l:min-l]在(V) / dot o(2)处进行2.5分钟的循环运动。吸气肌功要么1)处于控制水平[吸气食管压力（Pes）： -27.8 +/- 0.6 cmH（2)O], 2)通过比例辅助呼吸机减少（Pes: -16.3 +/- 0.5 cmH(2)O），要么3）通过阻力负荷增加（Pes: -35.6 +/- 0.8 cmH(2)O）。采用直接菲克法计算动脉血和混合静脉血O-2含量。在(V)超过o点（2max）时，对照试验和负荷试验的脑卒中容积、CO和肺o -2消耗(（V)超过o点(2)）没有差异（P > 0.05），但在(V)超过o点(2)时，吸气肌卸载比对照组低（分别为-8、-9和-7%）。动脉-混合静脉O-2差异在卸载或加载时没有变化。我们将这些发现与我们最近的研究相结合，表明在最大运动期间通常消耗的呼吸肌功对心血管系统有两个显着影响：1)高达14-16%的CO直接流向呼吸肌；2)局部反射性血管收缩显著影响流向腿部运动肌肉的血液。
We have recently demonstrated that changes in the work of breathing during maximal exercise affect leg blood flow and leg vascular conductance (C. A. Harms, M. A. Babcock, S. R. McClaran, D. F. Pegelow, G. A. Nickele, W. B. Nelson, and J. A. Dempsey. J. Appl. Physiol. 82: 1573-1583, 1997). Our present study examined the effects of changes in the work of breathing on cardiac output (CO) during maximal exercise. Eight male cyclists [maximal O-2 consumption ((V) over dot o(2max)): 62 +/- 5 ml kg-l:min-l] performed repeated 2.5-min bouts of cycle exercise at (V) over dot o(2). Inspiratory muscle work was either 1) at control levels [inspiratory esophageal pressure (Pes): -27.8 +/- 0.6 cmH(2)O], 2) reduced via a proportional-assist ventilator (Pes: -16.3 +/- 0.5 cmH(2)O), or 3) increased via resistive loads (Pes: -35.6 +/- 0.8 cmH(2)O). O-2 contents measured in arterial and mixed venous blood were used to calculate CO via the direct Fick method. Stroke volume, CO, and pulmonary O-2 consumption ((V) over dot o(2)) were not different (P > 0.05) between control and loaded trials at (V) over dot o(2max) but were lower (-8, -9, and -7%, respectively) than control with inspiratory muscle unloading at (V) over dot o(2). The arterial-mixed venous O-2 difference was unchanged with unloading or loading. We combined these findings with our recent study to show that the respiratory muscle work normally expended during maximal exercise has two significant effects on the cardiovascular system: 1) up to 14-16% of the CO is directed to the respiratory muscles; and 2) local reflex vasoconstriction significantly compromises blood flow to leg locomotor muscles.