Biophysics and Biomedical Modeling Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts;
Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts.
J Appl Physiol (1985). 2017 Nov 1;123(5):1214-1227. doi: 10.1152/japplphysiol.00344.2017. Epub 2017 Jul 13.
This study examined whether normobaric hypoxia (NH) treatment is more efficacious for sustaining high-altitude (HA) acclimatization-induced improvements in ventilatory and hematologic responses, acute mountain sickness (AMS), and cognitive function during reintroduction to altitude (RA) than no treatment at all. Seventeen sea-level (SL) residents (age = 23 ± 6 yr; means ± SE) completed in the following order: ) 4 days of SL testing; ) 12 days of HA acclimatization at 4,300 m; ) 12 days at SL post-HA acclimatization (Post) where each received either NH ( = 9, [Formula: see text] = 0.122) or Sham ( = 8; [Formula: see text] = 0.207) treatment; and ) 24-h reintroduction to 4,300-m altitude (RA) in a hypobaric chamber (460 Torr). End-tidal carbon dioxide pressure ([Formula: see text]), hematocrit (Hct), and AMS cerebral factor score were assessed at SL, on HA2 and HA11, and after 20 h of RA. Cognitive function was assessed using the SynWin multitask performance test at SL, on HA1 and HA11, and after 4 h of RA. There was no difference between NH and Sham treatment, so data were combined. [Formula: see text] (mmHg) decreased from SL (37.2 ± 0.5) to HA2 (32.2 ± 0.6), decreased further by HA11 (27.1 ± 0.4), and then increased from HA11 during RA (29.3 ± 0.6). Hct (%) increased from SL (42.3 ± 1.1) to HA2 (45.9 ± 1.0), increased again from HA2 to HA11 (48.5 ± 0.8), and then decreased from HA11 during RA (46.4 ± 1.2). AMS prevalence (%) increased from SL (0 ± 0) to HA2 (76 ± 11) and then decreased at HA11 (0 ± 0) and remained depressed during RA (17 ± 10). SynWin scores decreased from SL (1,615 ± 62) to HA1 (1,306 ± 94), improved from HA1 to HA11 (1,770 ± 82), and remained increased during RA (1,707 ± 75). These results demonstrate that HA acclimatization-induced improvements in ventilatory and hematologic responses, AMS, and cognitive function are partially retained during RA after 12 days at SL whether or not NH treatment is utilized. This study demonstrates that normobaric hypoxia treatment over a 12-day period at sea level was not more effective for sustaining high-altitude (HA) acclimatization during reintroduction to HA than no treatment at all. The noteworthy aspect is that athletes, mountaineers, and military personnel do not have to go to extraordinary means to retain HA acclimatization to an easily accessible and relevant altitude if reexposure occurs within a 2-wk time period.
本研究旨在探讨常压低氧（NH）治疗是否比不治疗更能有效维持高空（HA）适应引起的通气和血液学反应、急性高原病（AMS）和认知功能的改善，以及在重新进入高原（RA）期间。17 名海平面（SL）居民（年龄=23±6 岁；平均值±SE）按以下顺序完成：）4 天的 SL 测试；）在 4300 米处进行 12 天的 HA 适应；）HA 适应后 12 天在 SL 下（Post），其中每个接受 NH（=9，[公式：见文本] = 0.122）或 Sham（=8；[公式：见文本] = 0.207）治疗；）在减压室（460 托）中 24 小时重新引入 4300 米海拔高度（RA）。在 SL、HA2 和 HA11 以及 RA 后 20 小时评估呼气末二氧化碳分压（[公式：见文本]）、红细胞压积（Hct）和 AMS 大脑因子评分。使用 SynWin 多任务表现测试在 SL、HA1 和 HA11 以及 RA 后 4 小时评估认知功能。NH 和 Sham 治疗之间没有差异，因此数据合并。[公式：见文本]（mmHg）从 SL（37.2±0.5）下降到 HA2（32.2±0.6），进一步下降到 HA11（27.1±0.4），然后从 HA11 升高在 RA（29.3±0.6）期间。Hct（%）从 SL（42.3±1.1）增加到 HA2（45.9±1.0），从 HA2 再次增加到 HA11（48.5±0.8），然后从 HA11 减少在 RA（46.4±1.2）期间。AMS 患病率（%）从 SL（0±0）增加到 HA2（76±11），然后在 HA11 下降（0±0），并在 RA 期间保持降低（17±10）。SynWin 分数从 SL（1,615±62）下降到 HA1（1,306±94），从 HA1 增加到 HA11（1,770±82），并在 RA 期间保持增加（1,707±75）。这些结果表明，无论是否进行 NH 治疗，在 SL 下 12 天后重新进入 HA 期间，HA 适应引起的通气和血液学反应、AMS 和认知功能的改善部分得到维持。本研究表明，在海平面（SL）上进行为期 12 天的常压低氧治疗，在重新进入 HA 期间维持 HA 适应的效果并不优于完全不治疗。值得注意的是，如果在 2 周内重新暴露，运动员、登山者和军人不必采取特殊措施来维持对易于到达和相关海拔高度的 HA 适应。
