Department of Physiology, Showa University School of Medicine, Tokyo, Japan.
Respir Physiol Neurobiol. 2013 Apr 1;186(2):155-63. doi: 10.1016/j.resp.2013.01.008. Epub 2013 Jan 24.
Automatic regulation of tidal volume (VT) maintains CO2 homeostasis when spontaneous respiratory rhythm is replaced with a cortically triggered rhythm. We examined whether automatic regulation of respiratory frequency (fR) could maintain CO2 homeostasis at rest if the VT is cortically designated in experiments performed in 21 conscious humans. First, volitionally controlled fR at levels lower than baseline resulted in a larger VT, maintaining end-tidal CO2 fraction constant at eupneic levels. However, when fR was volitionally controlled at levels higher than baseline, end-tidal CO2 fraction decreased unexpectedly. Next, when the VT was volitionally constrained but fr was freely chosen, end-tidal CO2 fraction decreased. The present study revealed some limitations in the control of CO2 homeostasis by automatic regulation of fR, probably because respiratory rhythm is susceptible to non-metabolic factors. This study also showed the importance of automatic regulation of VT in maintaining CO2 homeostasis at rest. Nevertheless, automatic regulation of VT was incomplete when fR was volitionally imposed at high levels.
当自主呼吸节律被皮质触发节律取代时，潮气量（VT）的自动调节可维持二氧化碳的体内平衡。我们研究了在 21 名清醒的人类中进行的实验中，如果 VT 是皮质指定的，那么自动调节呼吸频率（fR）是否可以在休息时维持二氧化碳的体内平衡。首先，与基线水平相比，低于基线水平的自主控制的 fR 导致 VT 更大，从而使呼气末二氧化碳分数保持在正常通气水平。然而，当 fR 被自主控制在高于基线的水平时，呼气末二氧化碳分数出人意料地下降。接下来，当 VT 被自主限制但 fr 被自由选择时，呼气末二氧化碳分数下降。本研究揭示了自动调节 fR 对二氧化碳体内平衡控制的一些局限性，可能是因为呼吸节律易受非代谢因素的影响。本研究还表明了自动调节 VT 在维持休息时二氧化碳体内平衡中的重要性。然而，当 fR 被强制置于高水平时，VT 的自动调节并不完全。
