Rapid decompression to 50,000 feet: effect on heart rate response.
Interest in Molecular Sieve Oxygen Generation Systems (MSOGS) for use in military aircraft has demonstrated a need to study physiological effects of MSOGS product gas in the worst case scenario, a rapid decompression (RD). In this paper we report the heart rate (HR) response to positive pressure breathing (PPB) during and after RD from 6,096 to 15,239 m (20,000 to 50,000 ft) in a hypobaric chamber while breathing gas mixtures that simulate the product gas from MSOGS. Interbeat (R-R) intervals were recorded in 10 subjects while they breathed either Aviators' Breathing Oxygen (ABO), that is 99.5% oxygen, or 93% oxygen at two regulator settings: dilution and non-dilution. Additional experimental profiles on six subjects isolated the effects of hypoxia, anxiety, and PPB on HR changes after RD. Anxiety appeared to have the greatest effect. Most of the subjects showed increased HR and reduced HR variability after the onset of pressure breathing (immediately after decompression). As the exposure continued, HR variability increased as the HR began to decline. No consistent change in the HR response could be attributed to the modest increase in hypoxia produced by substitution of 93% oxygen for ABO.
Crew Technology Division, USAF School of Aerospace Medicine, Brooks AFB, TX 78235-5301.
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Chopp
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Bomar
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Harding
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Holden
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Bauer
D000328:Adult; D000337:Aerospace Medicine; D000531:Altitude; D001007:Anxiety / Q000209:etiology; D003664:Decompression; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D006931:Hyperbaric Oxygenation; D008297:Male; D008889:Military Personnel; D010100:Oxygen / Q000008:administration & dosage; D011175:Positive-Pressure Respiration; D013315:Stress, Psychological / Q000209:etiology
D010100:Oxygen