Differences in Cardio-Ventilatory Responses to Hypobaric and Normobaric Hypoxia: A Review
Richard NA, Koehle MS. Differences in cardio-ventilatory responses to hypobaric and normobaric hypoxia: a review. Aviat Space Environ Med 2012; 83:677–84.
The presence of differences in physiological response to a lowered inspired Po2 mediated by hypobaric hypoxia (HH) or normobaric hypoxia (NH) is controversial. This review examines the brief, acute, and subacute respiratory, cardiovascular, and subjective symptom response to intermediate and severe hypoxic exposure in NH and HH. Brief exposures lead to similar physiological responses; this is not the case in acute/subacute exposures. Extrapolating data from NH studies to HH in longer exposures is inappropriate as physiological responses to hypoxia seem to be influenced by the prevailing ambient pressure, especially in chronic exposures where acute mountain sickness severity is greater in HH than NH. Explanations for the discrepancy between the two modalities include differences in ventilatory patterns, alveolar gas disequilibrium, and dissimilar acute hypoxic ventilatory responses. Awareness and consideration of these key differences between NH and HH is essential to their proper application to kinesiology, altitude, and aviation medicine.
The presence of differences in physiological response to a lowered inspired Po2 mediated by hypobaric hypoxia (HH) or normobaric hypoxia (NH) is controversial. This review examines the brief, acute, and subacute respiratory, cardiovascular, and subjective symptom response to intermediate and severe hypoxic exposure in NH and HH. Brief exposures lead to similar physiological responses; this is not the case in acute/subacute exposures. Extrapolating data from NH studies to HH in longer exposures is inappropriate as physiological responses to hypoxia seem to be influenced by the prevailing ambient pressure, especially in chronic exposures where acute mountain sickness severity is greater in HH than NH. Explanations for the discrepancy between the two modalities include differences in ventilatory patterns, alveolar gas disequilibrium, and dissimilar acute hypoxic ventilatory responses. Awareness and consideration of these key differences between NH and HH is essential to their proper application to kinesiology, altitude, and aviation medicine.
Keywords: CO2; acute mountain sickness; hypobaric; hypoxia; normobaric; ventilation
Document Type: Research Article
Publication date: 01 July 2012
- The peer-reviewed monthly journal, Aviation, Space, and Environmental Medicine (ASEM) provides contact with physicians, life scientists, bioengineers, and medical specialists working in both basic medical research and in its clinical applications. It is the most used and cited journal in its field. ASEM is distributed to more than 80 nations.
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