背景:暴露于中等水平的模拟缺氧相对于地面水平具有微妙的认知作用,在健康的个体中。然而,关于缺氧和部分睡眠剥夺相结合的认知后果的数据很少,这是典型的军事或民用作战环境。在这项研究中,我们检验了一个假设,即在睡眠受限的情况下暴露于中度缺氧会损害认知的几个领域,我们还评估了皮质醇和α-淀粉酶的生理参数和唾液浓度。
方法:17名健康男性在常压低氧状态下(FIO2=13.6%,暴露30分钟(T+30')和4小时(T+240')后,完成了两次认知测试(使用PVT精神运动警觉任务的持续注意力和使用Go-NoGo抑制任务和N-Back工作记忆任务的执行功能)。3500米)(HY)。这是在一个晚上的睡眠限制(凌晨3点至凌晨6点睡前,SRHY)和一晚上的习惯性睡眠(晚上10点至凌晨6点睡前,HSHY)(具有交叉随机化)。分析了T30'和T240'会话期间的两晚睡眠结构和生理参数(氧饱和度(SpO2)和心率(HR)。在缺氧前分析唾液皮质醇和α-淀粉酶(sAA)浓度,在T+30'和T+240'认知会话之后,离开缺氧帐篷后.
结果:持续关注(RT和PVT中的失误次数)和执行功能(Go-NoGo和1-Back和2-Back参数,与HSHY相比,SRHY条件下的抑制和工作记忆特征)受损。与HSHY条件下缺氧30分钟相比,4小时后SpO2和HR更高,而仅在SRHY条件下HR在统计学上较高。在SRHY,唾液AA浓度低于HSHY,皮质醇高于HSHY。与30分钟时相比,在缺氧暴露4小时的认知会话后观察到sAA浓度显着增加,仅在SRHY条件下。在两种睡眠条件下,执行任务的反应时间与相应的心率(生理压力的非侵入性标志)之间存在显着正相关。没有观察到sAA和皮质醇的唾液水平,交感神经肾上腺髓系统和下丘脑-垂体肾上腺皮质系统各自的可靠指标。
结论:暴露于中度常压缺氧(模拟3,500米/11,500英尺)后,一个晚上3小时的睡眠会损害30分钟和4小时的认知能力。当暴露于中度缺氧伴睡眠限制时,导致认知障碍的关键决定因素和/或机制,特别是在执行功能上,尚未阐明。
BACKGROUND: Exposure to moderate levels of simulated hypoxia has subtle cognitive effects relative to ground level, in healthy individuals. However, there are few data on the cognitive consequences of the combination of hypoxia and partial sleep deprivation, which is a classic military or civilian operational context. In this study, we tested the hypothesis that exposure to moderate hypoxia while sleep-restricted impairs several domains of cognition, and we also assessed physiological parameters and salivary concentrations of cortisol and alpha-amylase.
METHODS: Seventeen healthy males completed two sessions of cognitive tests (sustained attention using the PVT psychomotor vigilance task and executive functions using the Go-NoGo inhibition task and N-Back working memory task) after 30 minutes (T+30\') and 4 hours (T+240\') of exposure in a normobaric hypoxic tent (FIO2 = 13.6%, ≃ 3,500 m) (HY). This was completed after one night of sleep restriction (3 a.m. to 6 a.m. bedtime, SRHY) and one night of habitual sleep (10 p.m. to 6 a.m. bedtime, HSHY) (with cross-over randomization). The two nights sleep architecture and physiological parameters (oxygen saturation (SpO2) and heart rate (HR) during T+30\' and T+240\'sessions were analyzed. Salivary cortisol and alpha-amylase (sAA) concentrations were analyzed before hypoxia, after the T+30\' and T+240\' cognitive sessions, and after leaving the hypoxic tent.
RESULTS: Sustained attention (RT and number of lapses in the PVT) and executive functions (Go-NoGo and 1-Back and 2-Back parameters, as inhibition and working memory signatures) were impaired in the SRHY condition compared to HSHY. SpO2 and HR were higher after 4 hours compared with 30 minutes of hypoxia in the HSHY condition, while only HR was statistically higher in the SRHY condition. In SRHY, salivary AA concentration was lower and cortisol was higher than in HSHY. A significant increase in sAA concentration is observed after the cognitive session at 4 hours of hypoxia exposure compared to that at 30 minutes, only in the SRHY condition. There are significant positive correlations between reaction time and the corresponding heart rate (a non-invasive marker of physiological stress) for the executive tasks in the two sleep conditions. This was not observed for salivary levels of sAA and cortisol, respective reliable indicators of the sympathoadrenomedullary system and the hypothalamic-pituitary adrenocortical system.
CONCLUSIONS: Exposure to moderate normobaric hypoxia (≃ 3,500 m / ≃ 11,500 ft simulated) after a single night of 3-hour sleep impairs cognitive performance after 30 minutes and 4 hours of exposure. The key determinants and/or mechanism(s) responsible for cognitive impairment when exposed to moderate hypoxia with sleep restriction, particularly on the executive function, have yet to be elucidated.