Operation Everest Ill (COMEX '97): effects of prolonged and progressive hypoxia on humans during a simulated ascent to 8,848 m in a hypobaric chamber.

Exposure to high altitude induces physiological or pathological modificationsthat are not always clearly attributable to a specific environmental factor:hypoxia, cold, stress, inadequate food. The principal goal of hypobaric chamberstudies is to determine the specific effect of hypoxia. Eight male volonteers( « altinauts » ), aged 23 to 37 were selected. They were first pre-acclimatized inthe Vallot Observatory (4,350m) before entering the chamber. The chamberwas progressively (30 days) decompressed down to 253 mmHg barometricpressure, with a recovery period of 3 days at 5,000m in the middle of thedecompression period. Eighteen protocoles were organized by 14 europeanteams, exploring the limiting factors of physical and psychological performance,and pathophysiology of acute mountain sickness (AMS). Ali subjects reached8,000m and 7 of them reached the simulated altitude of 8,848m. Threealtinauts complained with transient neurological symptoms which resignedrapidly with reoxygenation. Body weight decreased by 5.4 kg through anegative calorie balance. Four days only after the return to sea-level, subjectshad recovered 3.4 kg, i.e. 63% of the total loss. At 8,848m, mean SaO2 was68±3 %, PaO2 34 ± 4 mmHg, PCO2 12 ± 2 mmHg, pH 7,57 ± 0.02. Hemoglobinconcentration increased from 14.8 ± 1.4 to 18.4 ± 1.5 g/dl at 8000m andrecovered within 4 days at sea-level. AMS score increased rapidly at 6000mand was maximal at 7000m, especially for sleep. AMS was related to alterationin color vision and elevation of body temperatue. VO2max decreased by 59% at7000m. The purpose of this paper is to give a general description of the studyand the time course of main clinical and physiological parameters. Thealtinauts reached the "summit" (for some of them three consecutive times) inbetter physiological conditions than it would have been possible in themountains, probably because acclimatization and other environmental factorssuch as cold and nutrition were controlled

Operation Everest III (COMEX '97): Effects Of Prolonged And Progressive Hypoxia On Humans During A Simulated Ascent To 8,848 M In A Hypobaric Chamber

International audienceExposure to high altitude induces physiological or pathological modificationsthat are not always clearly attributable to a specific environmental factor:hypoxia, cold, stress, inadequate food. The principal goal of hypobaricchamber studies is to determine the specific effect of hypoxia. Eight malevolunteers ("altinauts"), aged 23 to 37 were selected. They were first preacclimatizedin the Observatoire Vallot (4,350m) before entering the chamber.The chamber was progressively decompressed down to 253 mmHg barometricpressure, with a recovery period of 3 days at 5,000m in the middle of thedecompression period. They spent a total of 31 days in the chamber. Eighteenprotocols were organized by 14 European teams, exploring the limiting factorsof physical and psychological performance, and the pathophysiology of acutemountain sickness (AMS). Ali subjects reached 8,000m and 7 of them reachedthe simulated altitude of 8,848m. Three altinauts complained of transientneurological symptoms which resolved rapidly with reoxygenation. Bodyweight decreased by 5.4 kg through a negative calorie balance. Only four daysafter the retum to sea-level, subjects had recovered 3.4 kg, i.e. 63% of the totalloss. At 8,848m (n=5), PaO2 was 30.6 ± 1.4 mmHg, PCO2 11.9 ± 1.4 mmHg,pH 7.58 ± 0.02 (arterialized capillary blood). Hemoglobin conce_ntrationincreased from 14.8±1.4 to 18.4±1.5 g/dl at 8,000m and recovered within 4days at sea-level. AMS score increased rapidly at 6,000m and was maximal at7 ,000m, especially for sleep. AM~ was related to alteration in color vision andelevation of body temperature. V02w.x decreased by 59% at 7 ,O00m. The purpose of this paper is to give a general description of the study and the timecourse of the main clinicat and physiological parameters. The altinauts reachedthe "summit" (for some of them three consecutive times) in betterphysiological conditions than it would have been possible in the mountains,probably because acclimatization and other environmental factors such as coldand nutrition were controlled