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European Journal of Applied Physiology

, Volume 89, Issue 2, pp 122–126 | Cite as

Normo- and hypobaric hypoxia: are there any physiological differences?

  • Gustave SavoureyEmail author
  • Jean-Claude Launay
  • Yves Besnard
  • Angélique Guinet
  • Stéphane Travers
Article

Abstract

Since Bert (1878) and Barcroft (1925), studies on hypoxia are realized by lowering ambient O2 partial pressure (PO2) either by barometric pressure reduction (hypobaric hypoxia HH) or by lowering the O2 fraction (normobaric hypoxia NH). Today, a question is still debated: "are there any physiological differences between HH and NH for the same ambient PO2?" 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 PO2 equal to 120 hPa (4500 m). Cardioventilatory variables [breathing frequency (f), tidal volume (V t), minute ventilation (V̇E), O2 and CO2 end-tidal fractions or pressures (FETO2 and FETCO2 or PETO2 and PETCO2 respectively), heart rate (HR) and O2 arterial saturation by pulse oxymetry (SpO2)] were measured throughout the tests. At the end of the tests, arterial blood samples were taken to measure arterial blood gases [O2 and CO2 arterial partial pressures (PaO2 and PaCO2), pH and O2 arterial saturation (SaO2)]. Results show that during HH compared to NH, f is greater (P≤0.001), V t and V̇E under BTPS conditions are lower (P≤0.05), and FETO2 and FETCO2 are higher (P≤0.05). However, PETO2 does not change during the last 25 min of the tests, and neither does PETCO2 throughout the tests. HR is higher (P≤0.05) and SpO2 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 SaO2 is lower (P≤0.05). It is concluded that the physiological responses of humans submitted to an acute hypoxia at a PO2 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 O2 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.

Keywords

Altitude Altitude illnesses Human Hypobaric and normoxic hypoxia 

Notes

Acknowledgements

We gratefully thank Professor Pierre Dejours, Membre de l'Académie des Sciences de Paris for his help and for his acceptance to review this manuscript. The contributions of subjects, especially the subjects of the Mountain Club of the Essa Lyon-Bron, are acknowledged as well as the technical assistance of A-M. Hanniquet, F. Grimbert, S. Martin and J. Denis. A special recognition is given to Médecin général Jacques Bittel.

References

  1. Barcroft J (ed) (1925) Respiratory function of the blood, Part I. Cambridge University Press, New YorkGoogle Scholar
  2. Bert P (1878) La pression barométrique: recherches de physiologie expérimentale. Masson, Paris, p 1168Google Scholar
  3. Dejours P, Dejours S (1992) The effects of barometric pressure according to Paul Bert: the question today. Int J Sports Med 13 [Suppl. 1] S1–S5Google Scholar
  4. Dejours P, Puccinelli R, Armand J, Dicharry M (1965) Concept and measurement of ventilatory sensitivity to carbon dioxide. J Appl Physiol 20 (5):890–897PubMedGoogle Scholar
  5. Farhi LE, Rahn H (1960) Dynamics of changes in carbon dioxide stores. Anesthesiology 21 (6):604–614Google Scholar
  6. Levine BD, Kubo K, Kobayashi T, Fukushima M, Shibamoto T, Ueda G (1988) Role of barometric pressure in pulmonary fluid balance and oxygen transport. J Appl Physiol 64 (1):419–428CrossRefPubMedGoogle Scholar
  7. Loeppky JA, Scotto P, Roach RC (1996) Acute ventilatory response to simulated altitude, normobaric hypoxia, and hypobaria. Aviat Space Environ Med 67 (11):1019–1922PubMedGoogle Scholar
  8. Loeppky JA, Icenogle M, Scotto P, Robergs R, Hinghofer Szalkay H, Roach RC (1997) Ventilation during simulated altitude, normobaric hypoxia and normoxic hypobaria. Respir Physiol 107 (3):231–239CrossRefPubMedGoogle Scholar
  9. Roach RC, Loeppky JA, Robergs R, Maes D, Sandoval D, Letellier JP (1994) Fluid balance in humans at high altitude: does hypobaria plays a role ? [abstract] FASEB J 8(4):A553 Google Scholar
  10. Roach RC, Loeppky A (1995) Does hypobaria play a role in the development of the high altitude illnesses ? In: Sutton JR, Houston CS, Coates G (eds) Hypoxia and the brain. Queen City Printers, Burlington, Va., pp 277–283Google Scholar
  11. Roach RC, Loeppky JA, Icenogle MV (1996) Acute mountain sickness: increased severity during simulated altitude compared with normobaric hypoxia. J Appl Physiol 81 (5):1908–1910PubMedGoogle Scholar
  12. Saltzman HA, Salzano JV, Blenkarn GD, Kylstra JA (1971) Effects of pressure on ventilation and gas exchange in man. J Appl Physiol 30 (4):443–449PubMedGoogle Scholar
  13. Shams H, Powell FL, Hempleman SC (1990) Effects of normobaric and hypobaric hypoxia on ventilation and arterial blood gases in ducks. Respir Physiol 80 (2–3):163–170Google Scholar
  14. Tucker A, Reeves JT, Robertshaw D, Grover RF (1983) Cardiopulmonary response to acute altitude exposure: water loading and denitrogenation. Respir Physiol 54 (3):363–380PubMedGoogle Scholar
  15. Wagner PD (1977) Diffusion and chemical reaction in pulmonary gas exchange. Physiol Rev 57 (2):257–312PubMedGoogle Scholar

Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • Gustave Savourey
    • 1
    Email author
  • Jean-Claude Launay
    • 1
  • Yves Besnard
    • 1
  • Angélique Guinet
    • 1
  • Stéphane Travers
    • 1
  1. 1.Département des Facteurs humainsCentre de recherches du service de santé des arméesLa Tronche France

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