Accession Number : ADA188358

Title :   Acute Mountain Sickness at 4500 m is not Altered by Repeated Eight-Hour Exposures to 3200-3550 m Normobaric Hypoxic Equivalent,

Corporate Author : ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA

Personal Author(s) : Burse, Richard L ; Forte, Vincent A , Jr

PDF Url : ADA188358

Report Date : 10 Sep 1987

Pagination or Media Count : 32

Abstract : A lightweight device, designed to supply inspired air at 12.8% concentration(PO2 equivalent to 3900 m altitude) by recirculating a portion of each expired breath after CO2 removal was tested at sea-level for its ability to induce altitude acclimation. Twelve young men (experimental group) breathed from the device for 7.5-8 h each day for ten successive days. On the morning of day 1, inspired 02 concentrations averaged 12.8%, as intended, but increased by noontime and remained elevated thereafter. This raised the average hypoxic stimulus to 13.8 = 0.9% (pO2 equivalent to 3370 + or - 517 m altitude) for the entire ten-day period. Ten other young men (control group) breathed normoxic air from a placebo device of identical appearance on the same schedule. On the tenth day, both groups were exposed for two days to 4500 m altitude in hypobaric chamber to assess the effect of the treatment on acute mountain sickness (AMS). After the sea-level treatment, the experimental group showed no significant differences from control in resting ventilatory rate, respiratory frequency or end-tidal PO2, but end-tidal PCO2 was lower; there was no indication of hemoconcentration. It was clear that administering such a stimulus for 8 h each day, even for ten successive days, was not sufficient to induce any meaningful degree of acclimation to 4500 m or to induce any beneficial ventilatory or hematological responses to that altitude. Keywords: Stress(Physiology), Hypobaric conditions, High altitude.

Descriptors :   *ACCLIMATIZATION, *ALTITUDE SICKNESS, *BREATHING APPARATUS, BLOOD CELLS, FREQUENCY, HEMATOLOGY, HIGH ALTITUDE, HYPOBARIC CHAMBERS, HYPOBARIC CONDITIONS, HYPOXIA, LIGHTWEIGHT, RESPIRATION, SEA LEVEL, STIMULI, CONCENTRATION(CHEMISTRY), RESPONSE(BIOLOGY), STRESS(PHYSIOLOGY)

Subject Categories : Stress Physiology
      Life Support Systems

Distribution Statement : APPROVED FOR PUBLIC RELEASE