Hypoxic helium breathing does not reduce alveolar-arterial PO2 difference in the horse.
Abstract: In a previous study we evaluated the mechanism of alveolar-arterial PO2 (AaPO2) reduction when nitrogen is replaced with helium in normoxia (FIO2 = 0.21). The reduction in AaPO2 was not due to changes in VA/Q inequality, pulmonary O2 diffusing capacity, or cardiac output, but to more complete diffusion equilibration as a consequence of the higher ventilation and thus PAO2 (which reduced the average slope of the hemoglobin O2 dissociation curve (ODC), and thus enhanced diffusive equilibration). We hypothesized that hypoxic He/O2 breathing in contrast would not reduce the AaPO2 because PAO2 and PaO2, although higher with He than N2, would remain constrained to the linear region of the ODC. Breathing hypoxic gas mixtures did constrain the PAO2 to the linear region of the ODC, even when PAO2 was increased by He/O2 breathing. Thus, the average slope of the ODC did not change when He replaced N2 and this explains the lack of change in AaPO2, as hypothesized.
Publication Date: 1995-06-01 PubMed ID: 7481115DOI: 10.1016/0034-5687(94)00138-pGoogle Scholar: Lookup
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- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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The study investigates the effect of hypoxic helium breathing on alveolar-arterial oxygen partial pressure (PO2) difference in horses. The researchers found that, unlike in normoxic conditions, hypoxic helium breathing did not reduce the alveolar-arterial (Aa) PO2, due to the fact that PAO2 and PaO2 remain constrained to the linear region of the oxygen dissociation curve (ODC), regardless of its increase with helium.
Introduction and Hypothesis
- The research was primarily focused on evaluating the effect of hypoxic conditions (low levels of oxygen) on AaPO2 in horses when helium replaces nitrogen.
- The motivation behind this study stemmed from earlier research where it was found that AaPO2 reduction happened when nitrogen was replaced with helium under normoxic conditions (normal oxygen concentrations).
- However, in this case, the researchers hypothesized that introducing helium instead of nitrogen in hypoxic environments would not demonstrate a reduction in AaPO2. This is due to the anticipatory constraints that are imposed on PAO2 and PaO2, which keep them in the linear region of the ODC.
Research Method and Outcomes
- Research methodology involved creating conditions where horses breathed a hypoxic gas mixture.
- The results confirmed the hypothesis by showing that hypoxic helium breathing did place constraints on PAO2 and PaO2. These constraints kept both within the linear segment of the ODC, irrespective of the consequent increase that occurred as a result of helium/oxygen inhalation.
- As predicted, the unchanged average slope of the ODC explained the non-reduction in AaPO2 under hypoxic conditions when helium replaced nitrogen.
Concluding Summary
- In conclusion, the study shows that hypoxic helium breathing does not reduce the difference in oxygen partial pressure between alveoli and arteries (AaPO2) in horses, contrary to findings in normoxic conditions.
- This research extends our understanding of how gases interact and affect oxygen partial pressures in different environmental conditions and could have important implications for veterinary science and health, particularly concerning respiratory and cardiovascular conditions in equines.
Cite This Article
APA
Erickson BK, Seaman J, Kubo K, Hiraga A, Kai M, Yamaya Y, Wagner PD.
(1995).
Hypoxic helium breathing does not reduce alveolar-arterial PO2 difference in the horse.
Respir Physiol, 100(3), 253-260.
https://doi.org/10.1016/0034-5687(94)00138-p Publication
Researcher Affiliations
- Equine Research Institute, Japan Racing Association, Tokyo.
MeSH Terms
- Animals
- Helium / physiology
- Horses / physiology
- Hypoxia / physiopathology
- Oxygen / blood
- Partial Pressure
- Physical Conditioning, Animal / physiology
- Pulmonary Alveoli / blood supply
- Pulmonary Alveoli / physiology
- Pulmonary Circulation / physiology
- Pulmonary Gas Exchange
- Respiration / physiology
- Respiratory Mechanics
Grant Funding
- HL-17731 / NHLBI NIH HHS
Citations
This article has been cited 5 times.- Ohmura H, Mukai K, Takahashi Y, Takahashi T. Metabolomic analysis of skeletal muscle before and after strenuous exercise to fatigue. Sci Rep 2021 May 27;11(1):11261.
- Ohmura H, Mukai K, Matsui A, Takahashi T, Jones JH. Cardiopulmonary function during supramaximal exercise in hypoxia, normoxia and hyperoxia in Thoroughbred horses. J Equine Sci 2020;31(4):67-73.
- Ohmura H, Mukai K, Takahashi Y, Takahashi T, Jones JH. Hypoxic training increases maximal oxygen consumption in Thoroughbred horses well-trained in normoxia. J Equine Sci 2017;28(2):41-45.
- Ogawa T, Calbet JA, Honda Y, Fujii N, Nishiyasu T. The effects of breathing a helium-oxygen gas mixture on maximal pulmonary ventilation and maximal oxygen consumption during exercise in acute moderate hypobaric hypoxia. Eur J Appl Physiol 2010 Nov;110(4):853-61.
- Esposito F, Ferretti G. The effects of breathing He-O2 mixtures on maximal oxygen consumption in normoxic and hypoxic men. J Physiol 1997 Aug 15;503 ( Pt 1)(Pt 1):215-22.
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