Cheung Stephen S, Mutanen Niina E, Karinen Heikki M, Koponen Anne S, Kyröläinen Heikki, Tikkanen Heikki O, Peltonen Juha E
1 Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University , St. Catharines, Ontario, Canada .
High Alt Med Biol. 2014 Sep;15(3):331-40. doi: 10.1089/ham.2013.1153. Epub 2014 Sep 11.
We investigated the effects of chronic hypobaric hypoxic acclimatization, performed over the course of a 72-day self-supported Everest expedition, on ventilatory chemosensitivity, arterial saturation, and tissue oxygenation adaptation along with total hemoglobin mass (tHb-mass) in nine experienced climbers (age 37±6 years, [Formula: see text] 55±7 mL·kg(-1)·min(-1)).
Exercise-hypoxia tolerance was tested using a constant treadmill exercise of 5.5 km·h(-1) at 3.8% grade (mimicking exertion at altitude) with 3-min steps of progressive normobaric poikilocapnic hypoxia. Breath-by-breath ventilatory responses, Spo2, and cerebral (frontal cortex) and active muscle (vastus lateralis) oxygenation were measured throughout. Acute hypoxic ventilatory response (AHVR) was determined by linear regression slope of ventilation vs. Spo2. PRE and POST (<15 days) expedition, tHb-mass was measured using carbon monoxide-rebreathing.
Post-expedition, exercise-hypoxia tolerance improved (11:32±3:57 to 16:30±2:09 min, p<0.01). AHVR was elevated (1.25±0.33 to 1.63±0.38 L·min(-1.)%(-1) Spo2, p<0.05). Spo2 decreased throughout exercise-hypoxia in both trials, but was preserved at higher values at 4800 m post-expedition. Cerebral oxygenation decreased progressively with increasing exercise-hypoxia in both trials, with a lower level of deoxyhemoglobin POST at 2400, 3500 and 4800 m. Muscle oxygenation also decreased throughout exercise-hypoxia, with similar patterns PRE and POST. No relationship was observed between the slope of AHVR and cerebral or muscle oxygenation either PRE or POST. Absolute tHb-mass response exhibited great individual variation with a nonsignificant 5.4% increasing trend post-expedition (975±154 g PRE and 1025±124 g POST, p=0.17).
We conclude that adaptation to chronic hypoxia during a climbing expedition to Mt. Everest will increase hypoxic tolerance, AHVR, and cerebral but not muscle oxygenation, as measured during simulated acute hypoxia at sea level. However, tHb-mass did not increase significantly and improvement in cerebral oxygenation was not associated with the change in AHVR.
我们调查了在一次为期72天的自主攀登珠穆朗玛峰探险过程中进行的慢性低压低氧适应对9名经验丰富的登山者（年龄37±6岁，[公式：见正文]55±7 mL·kg(-1)·min(-1)）的通气化学敏感性、动脉血氧饱和度、组织氧合适应以及总血红蛋白量（tHb-mass）的影响。
使用在3.8%坡度下以5.5 km·h(-1)的恒定跑步机运动（模拟高原地区的运动强度）并逐步进行3分钟的常压变碳酸低氧试验来测试运动低氧耐受性。在整个过程中测量逐次呼吸的通气反应、血氧饱和度（Spo2）以及大脑（额叶皮质）和活跃肌肉（股外侧肌）的氧合情况。急性低氧通气反应（AHVR）通过通气量与Spo2的线性回归斜率来确定。在探险前和探险后（<15天），使用一氧化碳再呼吸法测量tHb-mass。
探险后，运动低氧耐受性提高（从11:32±3:57分钟提高到16:30±2:09分钟，p<0.01）。AHVR升高（从1.25±0.33 L·min(-1.)%(-1) Spo2升高到1.63±0.38 L·min(-1.)%(-1) Spo2，p<0.05）。在两次试验中，整个运动低氧过程中Spo2均下降，但在探险后4800米处保持在较高水平。在两次试验中，随着运动低氧程度的增加，大脑氧合逐渐下降，在2400米、3500米和4800米处，探险后脱氧血红蛋白水平较低。在整个运动低氧过程中，肌肉氧合也下降，前后模式相似。在探险前或探险后，均未观察到AHVR斜率与大脑或肌肉氧合之间的关系。绝对tHb-mass反应个体差异很大，探险后有不显著的5.4%的增加趋势（探险前为975±154克，探险后为1025±124克，p=0.17）。
我们得出结论，在攀登珠穆朗玛峰的探险过程中对慢性低氧的适应会增加低氧耐受性、AHVR以及大脑氧合，但不会增加肌肉氧合，这是在海平面模拟急性低氧过程中测量得到的。然而，tHb-mass没有显著增加，大脑氧合的改善与AHVR的变化无关。
