In vivo and in vitro CO2 titration curves in the rabbit: adaptation to hypercapnic conditions.

Arterial blood acid-base status of unanesthetized, unrestrained rabbits was studied during 6-12 hr of exposure to 7, 10 and 14.5% CO2. Most of the changes in blood acid-base status occurred during the first 20-60 min of exposure to hypercapnia and only minor changes occurred during the remaining exposure period (up to 12 hr). Blood buffer values obtained were not different from those reported for other terrestrial mammals. The whole body buffer values obtained here for the rabbit (0.58 nM H+/mmHg PCO2) is higher than that reported previously for man and dog. This relatively high whole body buffer value complies well with the high tolerance to CO2 reported for the rabbit.