PERIODIC BREATHING IN THE CROCODILE, CROCODYLUS-NILOTICUS - CONSEQUENCES FOR THE GAS-EXCHANGE RATIO AND CONTROL OF BREATHING

The ventilatory pattern in the Nile crocodile consists of episodes of breathing, interrupted by periods of breath‐holdin, the latter occupying 80% of total time during normal breathing at 25°C. End‐tidal gas composition varied with the periodic breathing but Po2 was always high (Po2<110 torr) and Pco2 low (Pco2<25 torr). The alveolar gas exchange ratio, RE, was very low during the non‐ventilatory periods (RE ≃ 0.5), but increased markedly during ventilation. Breathing of hypoxic and hypercapnic gases caused a pronounced decrease in the duration of breath‐holds. Hypercapnia decreased breathing frequency during ventilatory periods, but increased tidal volume. The results are discussed in relation to the practice of prolonged breath‐holding associated with diving in crocodiles. Copyright © 1979 Wiley‐Liss, Inc., A Wiley Company