目标:紧急医疗服务(EMS)提供者暂时上升到高海拔,以进行无压力且没有氧气补充设施的直升机在山区的主要任务和次要运输。脑氧饱和度的降低会导致急性暴露于高原期间注意力和反应时间以及护理质量的损害。
目的:本研究的主要目的是调查在急性暴露于高原期间补充氧气对直升机EMS(HEMS)提供者认知能力的影响。
方法:这种介入,随机化,控制,双盲,交叉临床试验于2021年10月进行。每次试验都使用相当于4000米的模拟海拔场景,其中志愿者在受控的环境舱中以4m/s的恒定上升速率暴露于低压缺氧,可复制,和安全的条件。审判可以随时自愿终止。纳入标准是年龄在18至60岁之间的急诊医疗服务和搜救服务成员以及美国麻醉师协会的身体状况等级I。
方法:每位参与者进行了2项试验,一种是在补充氧气的情况下暴露于高原(干预试验),另一种是在补充环境空气的情况下暴露于高原(对照试验)。
方法:测量包括外周血氧饱和度(SpO2),脑氧合(ScO2),呼吸和心率,精神运动警觉测验(PVT)数字符号替换测试(DSST),n-Back测试(2-BACK),沟槽板测试,以及关于主观表现的问卷调查,压力,工作量,积极和消极的影响。配对t检验用于比较条件(干预与控制)。使用广义估计方程(GEE)进一步分析数据。
结果:共有36名志愿者(30名男性;平均[SD]年龄,36[9]年;平均[SD]教育,17[4]年)接受了干预和对照试验。干预试验,与对照试验相比,具有较高的SpO2值(平均值[SD],97.9[1.6]%vs.86[2.3]%,t检验,p=0.004)和ScO2(平均值[SD],69.9[5.8]%与62.1[5.2]%,配对t检验,p=0.004)。与对照试验相比,干预试验在5分钟后对PVT的反应时间(RT)较短(平均值[SD],277.8[16.7]msvs.282.5[15.3]ms,配对t检验,p=0.006)和30分钟后(平均值[SD],276.9[17.7]msvs.280.7[15.0]ms,配对t检验,p=0.054)在高度。在控制其他变量的同时,SpO2每降低%,RT增加0.37ms.干预试验显示,正确反应的DSST数量明显较高(平均值[SD],1.2[3.2],配对t检验,p=0.035)。干预试验中的变量与对照试验中的DSST错误反应数相似,2-BACK,和沟槽板测试。
结论:这项随机临床试验发现,在急性暴露于4000m海拔期间,补充氧气可以改善HEMS提供者的认知能力。补充氧气的使用可以允许在HEMS提供者中保持注意力和及时反应。同一天反复的海拔上升的影响,剥夺睡眠,和额外的压力源应该调查。试验注册NCT05073406,ClinicalTrials.gov试验注册。
OBJECTIVE: Emergency medical services (EMS) providers transiently ascend to high altitude for primary missions and secondary transports in mountainous areas in helicopters that are unpressurised and do not have facilities for oxygen supplementation. The decrease in cerebral oxygen saturation can lead to impairment in attention and reaction time as well as in quality of care during acute exposure to altitude.
OBJECTIVE: The primary aim of the current
study was to investigate the effect of oxygen supplementation on cognitive performance in Helicopter EMS (HEMS) providers during acute exposure to altitude.
METHODS: This interventional, randomized, controlled, double-blind, cross-over clinical
trial was conducted in October 2021. Each
trial used a simulated altitude scenario equivalent to 4000 m, in which volunteers were exposed to hypobaric hypoxia with a constant rate of ascent of 4 m/s in an environmental chamber under controlled, replicable, and safe conditions. Trials could be voluntarily terminated at any time. Inclusion criteria were being members of emergency medical services and search and rescue services with an age between 18 and 60 years and an American Society of Anesthesiologists physical status class I.
METHODS: Each participant conducted 2 trials, one in which they were exposed to altitude with oxygen supplementation (intervention trial) and the other in which they were exposed to altitude with ambient air supplementation (control
trial).
METHODS: Measurements included peripheral oxygen saturation (SpO2), cerebral oxygenation (ScO2), breathing and heart rates, Psychomotor Vigilance Test (PVT), Digit-Symbol Substitution Test (DSST), n-Back test (2-BACK), the Grooved Pegboard test, and questionnaires on subjective performance, stress, workload, and positive and negative affect. Paired t-tests were used to compare conditions (intervention vs. control). Data were further analyzed using generalized estimating equations (GEE).
RESULTS: A total of 36 volunteers (30 men; mean [SD] age, 36 [9] years; mean [SD] education, 17 [4] years) were exposed to the intervention and control trials. The intervention trials, compared with the control trials, had higher values of SpO2 (mean [SD], 97.9 [1.6] % vs. 86 [2.3] %, t-test, p = 0.004) and ScO2 (mean [SD], 69.9 [5.8] % vs. 62.1 [5.2] %, paired t-test, p = 0.004). The intervention trials compared with the control trials had a shorter reaction time (RT) on the PVT after 5 min (mean [SD], 277.8 [16.7] ms vs. 282.5 [15.3] ms, paired t-test, p = 0.006) and after 30 min (mean [SD], 276.9 [17.7] ms vs. 280.7 [15.0] ms, paired t-test, p = 0.054) at altitude. While controlling for other variables, there was a RT increase of 0.37 ms for each % of SpO2 decrease. The intervention trials showed significantly higher values for DSST number of correct responses (with a difference of mean [SD], 1.2 [3.2], paired t-test, p = 0.035). Variables in the intervention trials were otherwise similar to those in the control trials for DSST number of incorrect responses, 2-BACK, and the Grooved Pegboard test.
CONCLUSIONS: This randomized clinical trial found that oxygen supplementation improves cognitive performance among HEMS providers during acute exposure to 4000 m altitude. The use of oxygen supplementation may allow to maintain attention and timely reaction in HEMS providers. The impact of repeated altitude ascents on the same day, sleep-deprivation, and additional stressors should be investigated.
Trial registration NCT05073406, ClinicalTrials.gov
trial registration.