Lovering Andrew T, Fraigne Jimmy J, Dunin-Barkowski Witali L, Vidruk Edward H, Orem John M
Texas Tech University School of Medicine, Department of Physiology, Lubbock, USA.
Sleep. 2003 Dec 15;26(8):961-7. doi: 10.1093/sleep/26.8.961.
Sleep is disturbed at high altitudes. Low PO2 levels at high altitude cause hyperventilation, which results in secondary hypocapnia (low PaCO2 levels). Thus, although sleep disruption at high altitudes is generally assumed to be caused by hypoxia, it may instead be the result of hypocapnia.
To determine whether hypocapnia disrupts sleep.
Four cats were studied for a total of 345 hours of sleep recordings. Two methods were used to test this idea. First we studied their sleep when the cats breathed oxygen concentrations (15% and 10%) equivalent to those at approximately 12,000 feet and 21,000 feet. Then we studied their sleep again in response to the same hypoxic stimuli but with CO2 added to the inspirate to maintain normal CO2 levels. Second, we used mechanical hyperventilation to vary the levels of CO2 while maintaining normal O2 levels.
Hypoxia (10% O2) decreased the amount of rapid eye movement sleep to about 20% of normal, and adding back CO2 restored rapid eye movement sleep to approximately 70% of normal. Periodic breathing and apneas were not observed during hypoxia in sleep. When mechanical hyperventilation lowered the CO2 to 85%, 75%, and 65% of normal, rapid eye movement sleep decreased progressively from a control level of 17% of total recording time to 12%, 7%, and 4%, respectively.
We conclude that hypocapnia rather than hypoxia may account for most of the sleep disturbance at high altitudes.
在高海拔地区睡眠会受到干扰。高海拔地区的低氧分压水平会导致过度通气，进而引发继发性低碳酸血症（低动脉血二氧化碳分压水平）。因此，尽管通常认为高海拔地区的睡眠中断是由缺氧引起的，但实际上可能是低碳酸血症的结果。
确定低碳酸血症是否会扰乱睡眠。
对四只猫进行了总共345小时的睡眠记录研究。使用了两种方法来验证这一观点。首先，当猫呼吸相当于海拔约12000英尺和21000英尺处的氧气浓度（15%和10%）时，研究它们的睡眠情况。然后，在相同的低氧刺激下，但在吸入气体中添加二氧化碳以维持正常的二氧化碳水平，再次研究它们的睡眠情况。其次，我们使用机械通气来改变二氧化碳水平，同时维持正常的氧气水平。
低氧（10%氧气）使快速眼动睡眠量减少至正常水平的约20%，添加二氧化碳后，快速眼动睡眠恢复至正常水平的约70%。睡眠期间低氧时未观察到周期性呼吸和呼吸暂停。当机械通气将二氧化碳水平降至正常水平的85%、75%和65%时，快速眼动睡眠从总记录时间的17%的对照水平分别逐渐降至12%、7%和4%。
我们得出结论，低碳酸血症而非缺氧可能是高海拔地区大多数睡眠干扰的原因。
