Scheid P, Lofaso F, Isabey D, Harf A
Département de Physiologie, Hôpital Henri Mondor, Créteil, France.
J Appl Physiol (1985). 1994 Aug;77(2):876-82. doi: 10.1152/jappl.1994.77.2.876.
To investigate ventilatory CO2 sensitivity during inspiratory pressure support (IPS), we administered inspiratory CO2 [fractional concn (FICO2) 0.01, 0.03, or 0.05] in eight normal subjects without (CTRL) or with (Pinsp) positive inspiratory airway pressure (5 or 10 cmH2O). At CTRL and low IPS, CO2 inhalation led to a significant increase in tidal volume (VT) with nearly identical slopes in the plot of VT vs. end-tidal PCO2. At the high IPS level, VT at FICO2 of 0 was significantly above the value at lower Pinsp and did not increase with CO2 unless FICO2 was elevated to > 0.03. There was very little effect of either Pinsp or FICO2 on respiratory frequency and respiratory timing. The data suggest that the CO2 sensitivity of ventilation is similar at low levels of IPS as during CTRL. However, at high levels of IPS, VT is determined largely by the passive inflation and, thus, independent of CO2. CO2 has to be elevated to increase the respiratory drive before VT becomes CO2 sensitive.
为研究吸气压力支持（IPS）期间的通气二氧化碳敏感性，我们在8名正常受试者中给予吸入二氧化碳（分数浓度[FICO2]为0.01、0.03或0.05），其中4名无（对照组）或有（吸气压力）气道正压（5或10 cmH2O）。在对照组和低IPS水平时，吸入二氧化碳导致潮气量（VT）显著增加，VT与呼气末PCO2的关系曲线斜率几乎相同。在高IPS水平时，FICO2为0时的VT显著高于较低吸气压力时的值，并且除非FICO2升高至>0.03，否则不会随二氧化碳增加。吸气压力或FICO2对呼吸频率和呼吸时间的影响很小。数据表明，低水平IPS时的通气二氧化碳敏感性与对照组相似。然而，在高水平IPS时，VT很大程度上由被动充气决定，因此与二氧化碳无关。在VT对二氧化碳敏感之前，必须提高二氧化碳水平以增加呼吸驱动力。
