摘要： 目的 研究急性轻、中度缺氧暴露对人的心理运动及视觉反应时的影响。 方法 利用低压舱模拟300 m (对照高度)、2800 m、3600 m、4400 m高度缺氧暴露1 h，考察了18 名健康男性青年被试者指叩测验、简单反应时和选择反应时的变化。结果 血氧饱和度（SaO₂）由地面对照值98%分别降至90%、82%和74%。2800 m 缺氧暴露1 h心理运动绩效的各个参数并无显著改变(P＞0.05)。3600 m缺氧暴露时选择反应时的平均反应时明显延长，运动绩效下降(P＜0.05)，且随着高度的增加以上影响进一步加重(P＜0.01)。而简单反应时和指叩测验的绩效暴露于4400 m时仍无显著改变(P＞0.05)。 结论 本研究的结果提示，急性缺氧暴露于2800 m高度1 h并未对心理运动产生严重影响，而暴露于3600 m以上高度时会对选择反应时等复杂反应产生负面影响，且随着高度的增加而加重

中图分类号：R852.11；R853文献标识码：A文章编号：1002-0837(2000)04-0235-05

Effects of Acute Exposure to Mild or Moderate Hypoxia on Human Psychomotor Performance and Visual-reaction Time

LI Xue-yiWU Xing-yuYANG Chang-binWU Yan-hong

（Department of Aerospace Medicine, Fourth Military Medical University, Xi'an 710032）

FU ChuanSHEN Xiao-feng

（Department of Steward Medicine, China Southwest Airlines,Chendu 610202）

Abstract: Objective The aim of this study was to determine whether psychomotor performance and visual reaction time were affected by acute exposure to mild or moderate hypoxia. Method Eighteen healthy male volunteers performed finger tapping, simple reaction time(SRT) and 4-choice reaction time(CRT) tests at simulated altitude of 300 m (control),2800 m, 3600 m and 4400 m for 1 h in a hypobaric chamber. Result SaO₂ decreased from 98%(control) to 90%,82% and 74% respectively at the various altitudes. All the performance parameters showed no significant change after exposure to 2800 m for 1 h relative to ground level(P＞0.05). However the mean reaction time of 4-CRT under 3600 m prolonged and performance decreased as compared with baseline value(P＜0.05), and the performance decreased further under 4400 m(P＜0.01). No significant difference was found in finger tapping and SRT even under exposure to 4400 m for 1 h.Furthermore, no decrease in correct rate were observed at any altitude (P＞0.05). Conclusion The results from this study demonstrated that there were no measurable impairment of visual reaction time and psychomotor performance under exposure to an altitude of 2800 m for 1 h. However, adverse effects on psychomotor performance were observed under 3600 m and over.

Key word：altitude hypoxia;simulated tests;psychomotor;reaction time;performance

It is well known that hypoxia disrupts intracellular process and impairs cellular function.Brain cells with a uniquely high oxygen demand are most susceptible to low oxygen tension.Intellectual impairment is an early sign of hypoxia, and it's particularly dangerous because its signs and symptoms do not usually cause discomfort or pain,making it unlikely that the individual could recognize his own disability: slow thinking,unreliable calculations,faulty memory,poor judgmentand delayed reaction time.As the information and decision-making processes in modern military flight systems have become more and more demanding than those in older systems,any of the above mentioned impairment in pilots could threaten flight safety.There are extensive highland regions in our country,with one sixth of these areas high above 3000 m.If man is to work and live in environments with reduced oxygen levels,the effects of hypoxia on human cognitive performance and the limit of altitude must be further assessed.Although the effects of hypoxia on various complex tasks have been studied extensively but there are conflicting results in the literature regarding the effect of hypobaric hypoxia on cognitive and psychomotor performance^［1～11］.Therefor,the present study was initiated to observe the effects of hypoxia on psychomotor performance and visual reaction time in order to get more knowledge regarding the prevention of human performance deficits during stay in hypobaric hypoxic environment.

Method

SubjectsThe subjects took part in this experiment were 18 healthy young male freshmen from Fourth Military Medical University(FMMU),aged between 17 and 18 years.All the subjects were non-smokers and non-drinkers with normal or corrected to normal visual acuity and normal color vision.They were normally resident at 300 m and none were acclimatized to plateau prior to this experiment.

Altitude SimulationThe tests were carried out in a hypobaric chamber afforded by Department of Aerospace Medicine (DAM),FMMU.The subjects were randomly exposed to four altitudes (300 m,2800 m,3600 m and 4400 m),meanwhile they were asked to perform the psychomotor tests twice in 1 h period at each altitude(5 and 60 min after ascenting to the prescribed altitude).9～11 min were needed to complete the tests.The order of exposure to the various altitudes was randomly chosen by the chamber operator and the subjects and experimenters inside the chamber were without knowledge of it.The project and experimental protocol were approved by the department of technology and engineering of the DAM.The altitude in hypobaric chamber ascended to the test's at a speed of 15 m/s and maintained it for 1 h.After having finished all the tests,the hypobaric chamber was recompressed to the ground level (300 m high above sea level in Xi'an) at a speed of 5 m/s.During the descent,subjects were told to swallow and do Valsalva maneuver to prevent otitic Barotrauma.The chamber was continuously ventilated with fresh air.Other environmental factor's score: noise 75 dB(A); temperature 20.4～25.1℃;relative humidity 25%～43% and light breeze.All subjects wore flight headgear and earplugs inside the chamber to reduce the distraction of noise.Tests were performed at 18:30～21:30 to eliminate influence of circadian rhythm.The time between every two ascents was longer than 48 h.

Experimental Design and Procedure

To get familiar with the environment and tests,prior to the experiment the subjects were briefly told about the purpose and process of the experiment and they practiced the doings in the tests for 1 wk in order to get the manipulation stable.Analysis of variance for repeated measurements was carried out to compare with the baseline value at 300 m to minimize the effects of other factors such as noise,fatigue,learning effects etc.To reduce errors,all the test operations were carried out in standard orders and with fixed apparatuses by a same instructor.The subjects SaO₂(Arterial oxyhemoglobin saturation) was monitored with a finger oximeter then the blood pressure and heart rate were measured after exposure to each altitude.

Psychomotor testsThe software of Computer-administered tests used in this trial for finger tapping,simple visual reaction time and 4-CRT tests as provided by the Department of Occupational Health,Shanghai Medical University^［12,13］.The tests were controlled by,and all data were recorded on a PC 486.Subjects were seated at a table on which a visual display unit was placed,45 cm away from the subjects.

Finger tapping test: The subject tapped a key (“enter”) as rapidly as possible with the preferred index finger.The number of taps was counted for 20 s automatically by the computer,each 20 s trial was followed by a rest of approximately 30 s ; then the test was repeated with the non-preferred hand.

Visual simple reaction time test: a red square(2c