Breathing movements in the frog Rana pipiens. II. The power output and efficiency of breathing | doi.page

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Breathing movements in the frog Rana pipiens. II. The power output and efficiency of breathing

Canadian Journal of Zoology1975Vol. 53(3), pp. 345–353

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Abstract

The work done by the buccal cavity during buccal and lung ventilation cycles has been estimated from measurement of the area enclosed by pressure–volume loops for each cycle. The loops cycled in an anticlockwise direction with respect to time during buccal cycles. On the other hand, pressure–volume loops from the lungs cycled clockwise, showing that work was being done on the lungs by the buccal pump. Inflation and deflation of the buccal cavity from a syringe, in curarized frogs, gave a clockwise loop enclosing about 5.5–6.5% of the area enclosed by a naturally generated loop of the same pressure and volume. However, inflation and deflation of the lungs gave a loop which enclosed an area virtually identical with that obtained from a normally generated sequence of lung inflation and deflation. The power output of the buccal pump was directly proportional to body weight, the major determinant of the former being the larger buccal volume rather than pressure change as body weight increased. The mechanical efficiency of the buccal pump varied from 0.4% to 16.2%, efficiency increasing with increased power output over most of the physiological range. Mean efficiency of all buccal movements was calculated to be 8% and, at this value of efficiency, oxygen consumption of the respiratory muscles was 0.89 ml O 2 100 g −1 min −1 . In Rana pipiens at rest the oxygen cost of breathing appears to be about 5% of the total resting metabolism.

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