Oxygen transport and cardiovascular function at extreme altitude: lessons from Operation Everest II

Operation Everest II was designed to examine the physiological responses to gradual decompression simulating an ascent of Mt Everest (8,848 m) to an inspired PO2 of 43 mmHg. The principal studies conducted were cardiovascular, respiratory, muscular-skeletal and metabolic responses to exercise. Eight...

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Bibliographic Details
Published in:International journal of sports medicine 1992-10, Vol.13 Suppl 1 (S 1), p.S13-S18
Main Authors: Sutton, J. R., Reeves, J. T., Groves, B. M., Wagner, P. D., Alexander, J. K., Hultgren, H. N., Cymerman, A., Houston, C. S.
Format: Article
Language:English
Subjects:
Adult
Aerospace Medicine
Altitude
Applied physiology
Biological and medical sciences
Cardiac Output - physiology
Cardiovascular Physiological Phenomena
Heart Rate - physiology
Human physiology applied to population studies and life conditions. Human ecophysiology
Humans
Lactates - blood
Male
Medical sciences
Mountaineering - physiology
Muscles - physiology
Oxygen - metabolism
Oxygen Consumption - physiology
Physical Endurance - physiology
Respiratory Physiological Phenomena
Space life sciences
Transports. Aerospace. Diving. Altitude
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Summary:Operation Everest II was designed to examine the physiological responses to gradual decompression simulating an ascent of Mt Everest (8,848 m) to an inspired PO2 of 43 mmHg. The principal studies conducted were cardiovascular, respiratory, muscular-skeletal and metabolic responses to exercise. Eight healthy males aged 21-31 years began the "ascent" and six successfully reached the "summit", where their resting arterial blood gases were PO2 = 30 mmHg and PCO2 = 11 mmHg, pH = 7.56. Their maximal oxygen uptake decreased from 3.98 +/- 0.2 L/min at sea level to 1.17 +/- 0.08 L/min at PIO2 43 mmHg. The principal factors responsible for oxygen transport from the atmosphere to tissues were (1) Alveolar ventilation--a four fold increase. (2) Diffusion from the alveolus to end capillary blood--unchanged. (3) Cardiac function (assessed by hemodynamics, echocardiography and electrocardiography)--normal--although maximum cardiac output and heart rate were reduced. (4) Oxygen extraction--maximal with PvO2 14.8 +/- 1 mmHg. With increasing altitude maximal blood and muscle lactate progressively declined although at any submaximal intensity blood and muscle lactate was higher at higher altitudes.
ISSN:0172-4622
1439-3964
DOI:10.1055/s-2007-1024580