| Sleep is necessary for people. An adult needs about 7-8h of sleep every day. Sleep deprivation (SD) often happens in modern life because of working, studying or keeping on duty at night. Continuous operation or sustained operation must produce sleep loss and fatigue, which lead to the change of functions of psychology and physics. Sleep deprivation can (1) increase mental "lapses" which have an impact on the speed and accuracy of responses; (2) reduces ability to acquire and recall information in complex task; (3) produces changes in brain activity associated with decreased alertness; (4) slow cognitive ability; (5) alter the states of mood; (6) change the motivation.Sleep deprivation countermeasures can be divided into two categories: those used before work and during rest periods (preventive strategies) and those used on the job (operational strategies). Preventive strategies include nap, schedule of work/rest, nutrition, and so on. Operational strategies include pharmacological methods, exercise, and so forth. At present, scientists believe that the use of stimulants at proper moment, with proper dose and proper method may be the best choice. However, when using stimulant, there is a contradiction which high dose could lead to a lot of side-effect, whereas low dose were not efficient. And domestic research in this field has just begun. Tomeet the needs of the future high-tech war, it is necessary to investigate whether the stimulants are effective and feasible to overcome the effects of sleep deprivation.High ground has an important tactical meaning. But there are few researches on continuous operation or sustained operation at high altitude. Much information of military importance about high altitude has been learned from mountain climbing expeditions and experimental studies. It is very necessary to research the efficient countermeasures on sleep deprivation on high altitude, because hypoxia and sleep deprivation can severely degrade military operations.Our aims are to study caffeine and/or placebo expectation as countermeasures for the effects of 30h sleep deprivation on 400m altitude, and to study two caffeine doses as countermeasures for the effects of 30h sleep deprivation on 2850m altitude.The research included two parts. The first study was carried out on 400m altitude; the second study was carried out on 2850m altitude.The first study employed a double-blind, within-subjects, counter balanced design. Study was composed of five trials. Each trial continued 30h sleep deprivation from 06:00 to 12:00 the next day. Subjects repeatedly finished psychological and physiological tests. The testing times were arranged at 02:00, 04:00, 06:00, 08:00 and 12:00. The tests include the letter cancellation test, the Stroop test, the work memory test, the continuous calculation test, the simple reaction time (SRT), the profile of mood states, blood and pulse. In first trial, we investigated the effects of 30h sleep deprivation. In second trial, subjects took caffeine 200mg at 24:00. In thirdtrial, subjects took placebo 200mg at 24:00. In forth trial, subjects took caffeine 200mg at 24:00 and 04:00 separately. In fifth trial, subjects took caffeine 200mg at 24:00 and placebo 200mg at 04:00. We told subjects that the drugs they took were all caffeine and that caffeine was a good drug as countermeasures for sleep deprivation, which can trigger expectation of caffeine.The second study was composed of three trials. Each trial continues 3 Oh sleep deprivation from 07:00 to 13:00 the next day. Because of time different, the time of tests and having drug was put off one hour. In first trial, subjects took placebo 200mg at 01:00 and 05:00 separately. In second trial, subjects took caffeine 200mg at 01:00 and placebo 200mg at 05:00. In third trial, subjects took caffeine 200mg at 01:00 and 05:00 separately. We had gotten baselines of all tests at 11:00 before study carry out. We told subjects that the drugs they took may be caffeine or placebo. But experimenters didn't know them. In this way, we...
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