Accessory Regulatory Mechanism of Respiration. 20

Abstract

The investigations of Heymans, 1 Schmidt, 2 Cromer and Ivy 3 and others have emphasized the importance of the nervous control of respiration. We wish to report the effects on respiration of denervating the sensory end organs in the aorta, carotid sinus and lungs.

In brief, in 25 dogs, under moderate morphine-barbital anesthesia, in which the region of the carotid sinuses was denervated, respiratory death occurred in 10 either immediately or within a few minutes, Eleven of the remaining 15 dogs died following section of the vagi near the jugular foramen. Similar deaths were obtained in 1 of the 2 rabbits and the 2 cats used. Of 4 dogs under ether anesthesia, 1 under moderate anesthesia died following denervation of the carotid sinus regions and vagotomy. The other 3, under light anesthesia, survived the procedure. Five of the 29 animals under barbital anesthesia also survived both procedures. However, in all the animals that survived a prolonged apnea was obtained.

These results suggested that the effect of denervation depends on the sensitivity of the respiratory center. The following observation strengthened this impression: a dog under moderate morphine-barbital anesthesia, after sectioning of the vagi and denervation of carotid sinus regions, developed protracted apnea accompanied by the usual drop in blood pressure. Immediately after apnea appeared, the tracheal cannula was connected with a spirometer containing 10% CO₂. Manual compression of the chest 3 times, one minute after the occurrence of apnea (so are to force the 10% CO₂-air mixture into the lung alveoli) caused an immediate resumption of breathing and restoration of blood pressure to its previous level. This state continued after ordinary air was substituted for the CO₂ rich mixture. The resumption of breathing in this case was not due to the manual compression because this procedure was tried with ordinary air without effect in many of the other dogs that died.