Fluctuations of arterial pH associated with the respiratory cycle in dogs.

It is generally accepted that hydrion concentration of the circulating arterial blood, serially examined in the same individual, is kept constant within a narrow limit of pH range1-4). However, it must be noted that there is some fluctuation in the concentration of alveolar CO2 during a respiratory cycle, and that this may lead to fluctuation in arterial pH. Though many studies have been made on the acid-base balance in the blood, little attention has been given to this possible fluctuation of arterial pH. Using our own glass electrode assembly which continuously records the pH of the circulating arterial blood, the present investigation was intended to detect the cyclic fluctuation of pH of the circulating arterial blood by changing rates and depths of respiration.