REGULATION OF RESPIRATION THE EFFECT UPON SALIVARY SECRETION OF AN INCREASED OXYGEN CONTENT OF THE INSPIRED AIR AND OF FORCED VENTILATION

¹ From the Department of Physiology of the University of Michigan, Ann Arbor, Michigan, and the Department of Physiology and Pharmacology of the University of Alberta, Edmonton, Alberta, Canada

When the submaxillary gland of the dog was made to secrete at a constant rate by the continuous intravenous injection of pilocarpine, increasing the oxygen content of the inspired air to 30, 50 or 100 per cent increased the rate of secretion. The increase tended to persist for some time after the breathing of room air was resumed. Breathing a high oxygen mixture usually slowed submaxillary blood volume flow and slightly lowered the blood pressure. It increased occasionally the depth of respiration. The decrease in blood flow persisted, as a rule, for some time after the breathing of room air was resumed, but blood pressure and respiration recovered promptly.

The common result of forced ventilation was a reduction in salivary secretion accompanied by a reduction in respiratory movements. Not infrequently forced ventilation of smaller magnitude was associated with a temporary augmentation of secretion. The diminution of secretion has been attributed to the alkaline effect of the blowing off of carbon dioxide. The temporary augmentation has been attributed to the opposing effect of improved oxidations. It has been pointed out, nevertheless, that other factors may have been involved.

If oxidations had been reduced markedly by prolonged low oxygen administration or relatively inadequate artificial ventilation with pneumothorax leading to accumulation of fixed acids in the body, salivary secretion increased despite the continuing reduction of oxidations possibly an account of the acidity. When such an increase in secretion had developed increasing the oxygen in the inspired air, possibly by the removal of the acids, slowed the secretion.