Poon C S, Ward S A, Whipp B J
J Appl Physiol (1985). 1987 Feb;62(2):551-60. doi: 10.1152/jappl.1987.62.2.551.
In five healthy subjects, we studied the effects of controlled mechanical unloading of the respiratory system on ventilatory control during moderate exercise, utilizing a modified positive-pressure ventilator (IEEE Trans. Biomed. Eng. BME-33: 361-365, 1986). We were especially interested in whether isocapnia was maintained when a portion of the normal ventilatory response to constant-load cycling was subserved by the ventilator. The mechanical unloading was achieved by "assisting" airflow throughout inspiration in a constant proportion to instantaneous flow. Two modest degrees of assistance (A1 = 1.5 and A2 = 3.0 cmH2O X l-1 X s) were imposed. The assistance caused minute ventilation (VE) to increase immediately (inspiratory time shortening and tidal volume rising) and end-tidal PCO2 (PETCO2) to fall. Some 10-15 s later, inspiratory occlusion pressure (P100) decreased, and in the new steady-state VE and PETCO2 were virtually restored to their control exercise levels. The modest residual hyperventilation [delta PETCO2 = -0.9 Torr (A1) and -1.6 Torr (A2)], which was not significant statistically, contrasted markedly with the much larger increase predicted for VE had there been no compensatory reduction in ventilatory drive (as evidenced by the fall in P100). Consistent with earlier studies utilizing resistive loading (J. Appl. Physiol. 35: 361-366, 1973 and Acta Physiol. Scand. 120: 557-565, 1984), these observations suggest that ventilatory drive during moderate exercise is controlled to compensate for modest changes in respiratory-mechanical load, so that VE is preserved at a level appropriate to metabolic rate or nearly so.
在五名健康受试者中，我们使用改良的正压呼吸机（《IEEE生物医学工程汇刊》，BME - 33: 361 - 365, 1986）研究了在适度运动期间呼吸系统的控制性机械卸载对通气控制的影响。我们特别感兴趣的是，当呼吸机承担了对恒定负荷运动的部分正常通气反应时，是否能维持等碳酸血症。通过在整个吸气过程中以与瞬时流量成恒定比例的方式“辅助”气流来实现机械卸载。施加了两种适度程度的辅助（A1 = 1.5和A2 = 3.0 cmH₂O·l⁻¹·s）。这种辅助导致分钟通气量（VE）立即增加（吸气时间缩短，潮气量增加），呼气末二氧化碳分压（PETCO₂）下降。大约10 - 15秒后，吸气阻断压（P100）降低，在新的稳态下，VE和PETCO₂实际上恢复到对照运动水平。适度的残余过度通气[ΔPETCO₂ = -0.9 Torr（A1）和 -1.6 Torr（A2）]，在统计学上不显著，与如果没有通气驱动的代偿性降低（如P100下降所证明）时预测的VE的大幅增加形成明显对比。与早期使用阻力负荷的研究（《应用生理学杂志》，35: 361 - 366, 1973和《生理学杂志》，120: 557 - 565, 1984）一致，这些观察结果表明，适度运动期间的通气驱动受到控制，以补偿呼吸机械负荷的适度变化，从而使VE维持在与代谢率相适应或接近相适应的水平。
