Cymerman A, Reeves J T, Sutton J R, Rock P B, Groves B M, Malconian M K, Young P M, Wagner P D, Houston C S
Altitude Research Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts.
J Appl Physiol (1985). 1989 May;66(5):2446-53. doi: 10.1152/jappl.1989.66.5.2446.
Chronic exposure to high altitude reduces maximal O2 uptake (VO2max). At extreme altitudes approaching the summit of Mt. Everest [inspiratory PO2(PIO2) = 43 Torr], mean VO2max have been determined to be 15.3 ml.kg-1.min-1 in two subjects who breathed 14% O2 at 6,300 m on Mt. Everest (West et al., J. Appl. Physiol. 54: 1188-1194, 1983). To provide a more complete description of performance near the limits of human tolerance to chronic hypoxia, we measured VO2max in volunteers in an altitude chamber before, during, and after a 40-day decompression to a barometric pressure (PB) of 240 Torr (PIO2 = 43 Torr). In five of eight subjects studied at sea level and PB of 464, 347, 289, and 240 Torr, VO2max was reduced from 4.13 to 1.17 l/min (49.1-15.3 ml.kg-1.min-1) in agreement with the prior study. Although the range decreased, the rank order among the subjects was preserved. Arterial O2 saturation at maximum effort decreased (46% by ear oximetry), but minute ventilation, respiratory frequency, and tidal volume did not. The highest minute ventilation (201 l/min BTPS) was observed at PB of 464 Torr. Arterial PCO2 in three subjects at PB of 240 Torr, at rest, and with maximum effort, averaged 10.3 and 9.6 Torr, respectively. Sustained hyperventilation was crucial to exercise performance during chronic, severe hypoxemia. VO2max was lower after altitude exposure compared with initial sea level values, indicating that exposure had not improved sea level exercise capacity.
长期暴露于高海拔环境会降低最大摄氧量（VO2max）。在接近珠穆朗玛峰峰顶的极端海拔高度[吸入氧分压（PIO2）=43托]时，两名在珠穆朗玛峰6300米处呼吸14%氧气的受试者的平均VO2max被测定为15.3毫升·千克-1·分钟-1（韦斯特等人，《应用生理学杂志》54:1188 - 1194，1983年）。为了更全面地描述人类对慢性缺氧耐受性极限附近的运动表现，我们在海拔舱中对志愿者进行了测量，在减压至气压（PB）为240托（PIO2 = 43托）的40天期间及前后测量了VO2max。在八名于海平面以及PB为464、347、289和240托时进行研究的受试者中，有五名受试者的VO2max从4.13升/分钟降至1.17升/分钟（49.1 - 15.3毫升·千克-1·分钟-1），这与先前的研究结果一致。尽管范围有所减小，但受试者之间的排名顺序得以保留。竭尽全力时的动脉血氧饱和度下降（经耳部血氧测定为46%），但分钟通气量、呼吸频率和潮气量并未下降。在PB为464托时观察到最高的分钟通气量（201升/分钟，体温、气压、饱和水蒸气压条件下）。三名受试者在PB为240托时，静息和竭尽全力时的动脉二氧化碳分压平均分别为10.3托和9.6托。在慢性、严重低氧血症期间，持续的过度通气对运动表现至关重要。与最初的海平面值相比，海拔暴露后VO2max较低，表明暴露并未提高海平面运动能力。
