Department of Medicine, University of California San Diego, La Jolla, 92093-0623, USA.
High Alt Med Biol. 2010 Summer;11(2):103-10. doi: 10.1089/ham.2009.1089.
The primary objective of the American Medical Research Expedition to Everest was to obtain information on human physiology at the highest possible altitude, including the Everest summit. An important data point was the barometric pressure on the summit, because this determines the inspired P(O(2)). The first measurement ever taken was 253.0 mmHg. Because modeling studies had shown that extreme hyperventilation was essential to reach these great altitudes, 34 alveolar gas samples were collected above an altitude of 8000 m, including 4 on the summit. These showed that hyperventilation reduced the alveolar P(CO(2)) to between 7 and 8 mmHg in one climber. An important finding was that alveolar P(O(2)) was defended at a value of about 35 mmHg by the increasing hyperventilation as the climbers ascended higher. Venous blood samples collected on two summiters gave a mean base excess of -7.2 meq.L(-1). Using the alveolar P(CO(2)) value, this gave an arterial pH of over 7.7, indicating an extreme degree of respiratory alkalosis. While climbing at an altitude of 8300 m, one summiter showed a respiratory frequency of 86 breaths.min(-1) and tidal volume of 1.26 L, indicating very rapid shallow breathing. Maximal oxygen consumption for the summit was derived by having well-acclimatized subjects exercise maximally at an altitude of 6300 m while breathing 14% oxygen. The V(O(2)) was just over 1 L.min(-1), which is sufficient to explain how exceptional humans can reach the summit without supplementary oxygen. In addition to the measurements at altitudes over 8000 m, data were obtained at two camps at 5400- and 6300-m altitude. These gave information on the control of ventilation, periodic breathing, blood physiology, cerebral function, and metabolism.
美国医学研究珠峰远征队的主要目标是在尽可能高的海拔上获取人体生理学信息，包括珠穆朗玛峰的信息。一个重要的数据点是山顶的气压，因为这决定了吸入的 P(O(2))。首次测量的数值为 253.0mmHg。由于模型研究表明，极度过度通气对于到达这些高海拔地区是必不可少的，因此在海拔 8000 米以上采集了 34 个肺泡气体样本，其中包括 4 个在山顶。这些样本表明，在一名登山者中，过度通气将肺泡 P(CO(2))降低到 7-8mmHg 之间。一个重要的发现是，随着登山者上升得更高，肺泡 P(O(2))通过不断增加的过度通气来维持在大约 35mmHg 的水平。在两名登顶者身上采集的静脉血样本给出的平均基础过剩值为-7.2meq.L(-1)。使用肺泡 P(CO(2))值，这给出了动脉 pH 值超过 7.7，表明存在极度呼吸性碱中毒。在海拔 8300 米处攀爬时，一名登顶者的呼吸频率为 86 次/分钟，潮气量为 1.26L，表明呼吸非常急促且浅。通过让适应良好的受试者在海拔 6300 米处最大程度地呼吸 14%的氧气来计算登顶时的最大氧气消耗。V(O(2))刚刚超过 1L.min(-1)，这足以解释为什么非凡的人类可以在没有补充氧气的情况下到达顶峰。除了在海拔 8000 米以上的测量外，还在海拔 5400-6300 米的两个营地获得了数据。这些数据提供了关于通气控制、周期性呼吸、血液生理学、大脑功能和代谢的信息。
