Burnet H, Reynaud-Gaubert M, Lucciano M, Jammes Y
Laboratoire de Biologie des Hautes pressions, URA 1330-CNRS, Faculté de Médecine-Nord, Marseille, France.
Respir Physiol. 1992 Dec;90(3):377-86. doi: 10.1016/0034-5687(92)90116-e.
When breathing room air at sea level the expired gas temperature (TE) increases in proportion to the inspired one (TI). Previous studies conducted under hyperbaric conditions have assumed that the TE vs TI relationship was the same when humans breathed room air at atmospheric pressure or helium-oxygen mixture under hyperbaric conditions. We hypothesized that the use of dilutant gases, as helium (He) or hydrogen (H2), having low density but high specific heat compared to nitrogen, could change the TE vs TI regression. The present study was conducted on 3 professional divers participating in the COMEX Hydra IX experiment. Three conditions were studied: A, (23.5 ATA, He-H2-O2 mixture); B, (21 ATA, H2-O2 mixture); and C, (21 ATA, He-O2 mixture). In each condition six different inspired temperatures were tested, while minute ventilation, TI and TE values were measured simultaneously. In all cases a linear relationship was found between TE and TI, but the slopes of the regression lines obtained in conditions A and B (gas mixture containing H2) were significantly lower than in condition C (He-O2 mixture). Computation of the convective respiratory heat loss (Cr) revealed that, when the subjects breathed the coldest gas mixtures (+10 degrees C), Cr value was 1.6 times higher in condition B than in C. These data are consistent with theoretical considerations and they demonstrate that a single equation cannot be used to predict the TE vs TI relationship in all environmental circumstances.
在海平面呼吸室内空气时，呼出气体温度（TE）与吸入气体温度（TI）成比例增加。以往在高压条件下进行的研究假定，当人类在常压下呼吸室内空气或在高压条件下呼吸氦氧混合气时，TE与TI的关系是相同的。我们推测，与氮气相比，使用密度低但比热容高的稀释气体，如氦气（He）或氢气（H2），可能会改变TE与TI的回归关系。本研究对3名参与COMEX Hydra IX实验的职业潜水员进行。研究了三种条件：A，（23.5个绝对大气压，氦 - 氢 - 氧混合气）；B，（21个绝对大气压，氢 - 氧混合气）；C，（21个绝对大气压，氦 - 氧混合气）。在每种条件下测试了六种不同的吸入温度，同时测量了分钟通气量、TI和TE值。在所有情况下，均发现TE与TI之间存在线性关系，但在条件A和B（含H2的气体混合物）中获得的回归线斜率明显低于条件C（氦 - 氧混合气）。对流呼吸热损失（Cr）的计算表明，当受试者呼吸最冷的气体混合物（+10摄氏度）时，条件B下的Cr值比条件C高1.6倍。这些数据与理论考虑一致，并且表明不能使用单一方程来预测所有环境情况下的TE与TI关系。
