Adaptive variation in the mammalian respiratory system in relation to energetic demand: VII. Flow of oxygen across the pulmonary gas exchanger

Richard H. Karas, C. Richard Taylor, James H. Jones, Stan L Lindstedt, R. Blake Reeves, Ewald R. Weibel

Research output: Contribution to journalArticle

49 Scopus citations


This paper addresses the question of whether the lung's gas exchange capacity limits O2 uptake in exercising animals. Physiological data measured whiel animals exercised at V̇O2 max are used together with morphometric data on the pulmonary diffusing capacity (DLO2 ) to calculate the change in O2 concentration and PO2 of the blood as it transits the lung. The 2.5-fold difference in V̇O2 max between the athletic dog and pony and the less athletic goat and calf was used to test for a match between structure and function at the level of O2 transfer in the lung. Since the 2.5-fold difference in V̇O2 max is not matched by a 2.5-fold difference in diffusing capacity of the lung for O2, we find that the less athletic species utilize only 1/3 of their capacity at V̇O2 max while the athletic species utilize 3/4. The excess diffusing capacity can be thought of as a 'safety factor' allowing animals to tolerate a decrease in PAO2 or DLO2 that may occur normally at altitude or during disease, but it is not clear why this factor should be smaller in the more athletic species.

Original languageEnglish (US)
Pages (from-to)101-115
Number of pages15
JournalRespiration Physiology
Issue number1
StatePublished - Jan 1 1987
Externally publishedYes



  • Bohr integration
  • Calves
  • Capillary transit time
  • Cardiac output
  • Dogs
  • Goats
  • Hypoxia
  • Lung
  • Morphometry
  • Ponies

ASJC Scopus subject areas

  • Physiology
  • Pulmonary and Respiratory Medicine

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