| Normo- and hypobaric hypoxia: are there any physiological differences? | |
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MedLine Citation:
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PMID: 12665974 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Since Bert (1878) and Barcroft (1925), studies on hypoxia are realized by lowering ambient O(2) partial pressure (PO(2)) either by barometric pressure reduction (hypobaric hypoxia HH) or by lowering the O(2) fraction (normobaric hypoxia NH). Today, a question is still debated: "are there any physiological differences between HH and NH for the same ambient PO(2)?" Since published studies are scarce and controversial, we submitted 18 subjects in a random order to a 40-min HH test and to a 40-min NH test at an ambient PO(2) equal to 120 hPa (4500 m). Cardioventilatory variables [breathing frequency (f), tidal volume (V(t)), minute ventilation (V(E)), O(2) and CO(2) end-tidal fractions or pressures (FET(O2) and FET(CO2) or PET(O2) and PET(CO2) respectively), heart rate (HR) and O(2) arterial saturation by pulse oxymetry (SpO(2))] were measured throughout the tests. At the end of the tests, arterial blood samples were taken to measure arterial blood gases [O(2) and CO(2) arterial partial pressures ( Pa(O2) and Pa(CO2)), pH and O(2) arterial saturation (SaO(2))]. Results show that during HH compared to NH, f is greater (P</=0.001), V(t) and V(E) under BTPS conditions are lower (P</=0.05), and FET(O2) and FET(CO2) are higher (P</=0.05). However, PET(O2) does not change during the last 25 min of the tests, and neither does PET(CO2) throughout the tests. HR is higher (P</=0.05) and SpO(2) lower (P</=0.05) in HH compared to NH. Arterial blood data reveal that hypoxemia, hypocapnia and blood alkalosis are greater in HH compared to NH and that SaO(2) is lower (P</=0.05). It is concluded that the physiological responses of humans submitted to an acute hypoxia at a PO(2) equal to 120 hPa differ according to the type of hypoxia. Compared to NH, HH leads to a greater hypoxemia, hypocapnia, blood alkalosis and a lower O(2) arterial saturation. These physiological differences could be the consequence of an increase in dead space ventilation, probably related to the barometric pressure reduction, and could be grouped together under the term "the specific response to hypobaric hypoxia". Knowledge of this specific response could improve the comprehension, prevention and treatment of altitude illnesses in the future. |
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Authors:
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Gustave Savourey; Jean-Claude Launay; Yves Besnard; Angélique Guinet; Stéphane Travers |
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Publication Detail:
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Type: Clinical Trial; Journal Article; Randomized Controlled Trial Date: 2003-02-11 |
Journal Detail:
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Title: European journal of applied physiology Volume: 89 ISSN: 1439-6319 ISO Abbreviation: Eur. J. Appl. Physiol. Publication Date: 2003 Apr |
Date Detail:
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Created Date: 2003-03-31 Completed Date: 2003-07-29 Revised Date: 2004-11-17 |
Medline Journal Info:
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Nlm Unique ID: 100954790 Medline TA: Eur J Appl Physiol Country: Germany |
Other Details:
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Languages: eng Pagination: 122-6 Citation Subset: IM |
Affiliation:
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Département des Facteurs humains, Centre de recherches du service de santé des armées, 38702 La Tronche cedex France. gsavourey@crssa.net |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Adult Anoxia / physiopathology* Atmospheric Pressure* Carbon Dioxide Humans Male Mouth / physiopathology Oxygen Partial Pressure Respiratory Mechanics Temperature Tidal Volume Time Factors |
| Chemical | |
Reg. No./Substance:
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124-38-9/Carbon Dioxide; 7782-44-7/Oxygen |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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