Sexton J, Mueller K, Elliott A, Gerzer D, Strohl K P
Case Western Reserve University, Cleveland, OH, USA.
Aviat Space Environ Med. 1998 Apr;69(4):387-90.
The purpose of the study was to determine whether chamber exposure to low levels of CO2 results in functional alterations in gas mixing and closing volume in humans. Four healthy volunteer subjects were exposed to 0.7% CO2 and to 1.2% CO2. Spirometry, lung volumes, single breath nitrogen washout, diffusing capacity for carbon monoxide (DLCO) by two methods, and cardiac output were measured in triplicate. Values were obtained over two non-consecutive days during the training period (control) and on days 2 or 3, 4, 6, 10, 13, and 23 of exposure to each CO2 level. Measurements were made during the same time of day. There was one day of testing after exposure, while still in the chamber but off carbon dioxide. The order of testing, up until measurements of DLCO and cardiac output, were randomized to avoid presentation effects. The consistent findings were a reduction in diffusing capacity for carbon monoxide and a fall in cardiac output, occurring to a similar degree with both exposures. For the group as a whole, there was no indication of major effects on spirometry, lung volumes, gas mixing or dead space. We conclude that small changes may occur in the function of distal gas exchanging units; however, these effects were not associated with any adverse health effects. The likelihood of pathophysiologic changes in lung function or structure with 0.7 or 1.2% CO2 exposure for this period of time, is therefore, low.
该研究的目的是确定人体在低水平二氧化碳环境中是否会导致气体混合功能改变和闭合气量变化。四名健康志愿者分别暴露于0.7%和1.2%的二氧化碳环境中。肺活量测定、肺容积、单次呼吸氮冲洗、两种方法测量的一氧化碳弥散量（DLCO）以及心输出量均进行了三次测量。在训练期（对照）的两个非连续日以及暴露于每种二氧化碳水平的第2或3、4、6、10、13和23天获取数值。测量在一天中的同一时间进行。暴露后在舱内但停止二氧化碳供应的情况下进行了一天的测试。在测量DLCO和心输出量之前，测试顺序是随机的，以避免呈现效应。一致的发现是一氧化碳弥散量降低和心输出量下降，两种暴露情况下的程度相似。对于整个组来说，没有迹象表明对肺活量测定、肺容积、气体混合或死腔有重大影响。我们得出结论，远端气体交换单位的功能可能会发生微小变化；然而，这些影响与任何不良健康影响无关。因此，在这段时间内暴露于0.7%或1.2%二氧化碳环境中导致肺功能或结构发生病理生理变化的可能性较低。
