Ottestad William, Hansen Tor Are, Pradhan Gaurav, Stepanek Jan, Høiseth Lars Øivind, Kåsin Jan Ivar
Norwegian Special Operations Command (NORSOC), Oslo, Norway;
Air Ambulance Department, Oslo University Hospital, Oslo, Norway.
J Appl Physiol (1985). 2017 Dec 1;123(6):1443-1450. doi: 10.1152/japplphysiol.00169.2017. Epub 2017 Aug 24.
High-Altitude High Opening (HAHO) is a military operational procedure in which parachute jumps are performed at high altitude requiring supplemental oxygen, putting personnel at risk of acute hypoxia in the event of oxygen equipment failure. This study was initiated by the Norwegian Army to evaluate potential outcomes during failure of oxygen supply, and to explore physiology during acute severe hypobaric hypoxia. A simulated HAHO without supplemental oxygen was carried out in a hypobaric chamber with decompression to 30,000 ft (9,144 m) and then recompression to ground level with a descent rate of 1,000 ft/min (305 m/min). Nine subjects were studied. Repeated arterial blood gas samples were drawn throughout the entire hypoxic exposure. Additionally, pulse oximetry, cerebral oximetry, and hemodynamic variables were monitored. Desaturation evolved rapidly and the arterial oxygen tensions are among the lowest ever reported in volunteers during acute hypoxia. Pa decreased from baseline 18.4 (17.3-19.1) kPa, 138.0 (133.5-143.3) mmHg, to a minimum value of 3.3 (2.9-3.7) kPa, 24.8 (21.6-27.8) mmHg, after 180 (60-210) s, [median (range)], = 9. Hyperventilation with ensuing hypocapnia was associated with both increased arterial oxygen saturation and cerebral oximetry values, and potentially improved tolerance to severe hypoxia. One subject had a sharp drop in heart rate and cardiac index and lost consciousness 4 min into the hypoxic exposure. A simulated high-altitude airdrop scenario without supplemental oxygen results in extreme hypoxemia and may result in loss of consciousness in some individuals. This is the first study to investigate physiology and clinical outcome of oxygen system failure in a simulated HAHO scenario. The acquired knowledge is of great value to make valid risk-benefit analyses during HAHO training or operations. The arterial oxygen tensions reported in this hypobaric chamber study are among the lowest ever reported during acute hypoxia.
高空高开伞（HAHO）是一种军事作战程序，即在高海拔地区进行跳伞，需要补充氧气，一旦氧气设备出现故障，人员就会面临急性缺氧的风险。这项研究由挪威军队发起，旨在评估氧气供应失败时的潜在后果，并探索急性严重低压缺氧期间的生理状况。在一个低压舱内进行了一次无补充氧气的模拟高空高开伞，减压至30000英尺（9144米），然后以每分钟1000英尺（305米）的下降速度重新加压至地面水平。对9名受试者进行了研究。在整个缺氧暴露过程中反复采集动脉血气样本。此外，还监测了脉搏血氧饱和度、脑血氧饱和度和血流动力学变量。氧饱和度迅速下降，动脉血氧张力是志愿者在急性缺氧期间报告的最低值之一。动脉血氧分压从基线的18.4（17.3 - 19.1）千帕，138.0（133.5 - 143.3）毫米汞柱，在180（60 - 210）秒后降至最低值3.3（2.9 - 3.7）千帕，24.8（21.6 - 27.8）毫米汞柱，[中位数（范围）]，n = 9。随后出现低碳酸血症的过度通气与动脉血氧饱和度和脑血氧饱和度值的增加相关，并可能提高对严重缺氧的耐受性。一名受试者在缺氧暴露4分钟时心率和心脏指数急剧下降并失去意识。无补充氧气的模拟高空空投场景会导致极度低氧血症，可能导致一些人失去意识。这是第一项在模拟高空高开伞场景中研究氧气系统故障的生理状况和临床结果的研究。所获得的知识对于在高空高开伞训练或行动期间进行有效的风险效益分析具有重要价值。在这个低压舱研究中报告的动脉血氧张力是急性缺氧期间报告的最低值之一。
