Lador Frédéric, Azabji Kenfack Marcel, Moia Christian, Cautero Michela, Morel Denis R, Capelli Carlo, Ferretti Guido
Département de Physiologie, Centre Médical Universitaire, 1 rue Michel Servet, 1211 Genève 4, Switzerland.
Am J Physiol Regul Integr Comp Physiol. 2006 Apr;290(4):R1071-9. doi: 10.1152/ajpregu.00366.2005. Epub 2005 Oct 20.
We tested whether the kinetics of systemic O(2) delivery (QaO(2)) at exercise start was faster than that of lung O(2) uptake (Vo(2)), being dictated by that of cardiac output (Q), and whether changes in Q would explain the postulated rapid phase of the Vo(2) increase. Simultaneous determinations of beat-by-beat (BBB) Q and QaO(2), and breath-by-breath Vo(2) at the onset of constant load exercises at 50 and 100 W were obtained on six men (age 24.2 +/- 3.2 years, maximal aerobic power 333 +/- 61 W). Vo(2) was determined using Grønlund's algorithm. Q was computed from BBB stroke volume (Q(st), from arterial pulse pressure profiles) and heart rate (f(h), electrocardiograpy) and calibrated against a steady-state method. This, along with the time course of hemoglobin concentration and arterial O(2) saturation (infrared oximetry) allowed computation of BBB QaO(2). The Q, QaO(2) and Vo(2) kinetics were analyzed with single and double exponential models. f(h), Q(st), Q, and Vo(2) increased upon exercise onset to reach a new steady state. The kinetics of QaO(2) had the same time constants as that of Q. The latter was twofold faster than that of Vo(2). The Vo(2) kinetics were faster than previously reported for muscle phosphocreatine decrease. Within a two-phase model, because of the Fick equation, the amplitude of phase I Q changes fully explained the phase I of Vo(2) increase. We suggest that in unsteady states, lung Vo(2) is dissociated from muscle O(2) consumption. The two components of Q and QaO(2) kinetics may reflect vagal withdrawal and sympathetic activation.
我们测试了运动开始时全身氧输送（QaO₂）的动力学是否比肺氧摄取（Vo₂）的动力学更快，后者是否由心输出量（Q）决定，以及Q的变化是否能解释Vo₂增加的假定快速阶段。在六名男性（年龄24.2±3.2岁，最大有氧功率333±61W）进行50W和100W恒定负荷运动开始时，同步逐搏（BBB）测定Q和QaO₂，并逐次呼吸测定Vo₂。Vo₂使用格伦德算法测定。Q由BBB每搏输出量（Q(st)，根据动脉脉搏压力曲线）和心率（f(h)，心电图）计算得出，并通过稳态方法进行校准。这与血红蛋白浓度和动脉血氧饱和度（红外血氧测定法）的时间进程一起，使得能够计算BBB QaO₂。使用单指数和双指数模型分析Q、QaO₂和Vo₂的动力学。运动开始时f(h)、Q(st)、Q和Vo₂增加，以达到新的稳态。QaO₂的动力学与Q具有相同的时间常数。后者比Vo₂快两倍。Vo₂的动力学比先前报道的肌肉磷酸肌酸减少的动力学更快。在两阶段模型中，由于菲克方程，I期Q变化的幅度完全解释了Vo₂增加的I期。我们认为，在非稳态下，肺Vo₂与肌肉氧消耗解离。Q和QaO₂动力学的两个组成部分可能反映迷走神经撤离和交感神经激活。
