A steady-state model of maximal oxygen and carbon dioxide transport in anuran amphibians

P.C. Withers, S.S. Hillman

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17 Citations (Scopus)


A steady-state model incorporting pulmonary ventilation, pulmonary diffusion capacity, cardiovascular transport capacity, and tissue diffusion capacity, was developed to describe the maximal O2 and CO2 transport capacity for an anuran amphibian (Bufo). Solution of the model by iterative calculation closely predicted 1) the empirical maximal O2 consumption (V̇O(2max) for Bufo, 2) variation in empirical V̇O(2max) for three other genera (Rana, Xenopus, Scaphiopus), and the empirically observed effects on V̇O(2max) of 3) hypobaric hypoxia, 4) artificially induced anemia, and 5) β-blockade of heart rate increment with activity. The model indicates that cardiovascular transport is the rate-limiting step to V̇O(2max) in amphibians and that an increase in circulatory O2 transport is a major physiological adaptation for increasing total aerobic capacity. CO2 transport and body fluid PCO2 values were primarily determined by pulmonary ventilatory capacity, and to a lesser extent by cardiovascular transport. The model should be generally applicable to other terrestrial vertebrates.
Original languageEnglish
Pages (from-to)860-868
Number of pages9
JournalJournal of Applied Physiology
Issue number2
Publication statusPublished - 1988


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