STUDIES ON DIFFUSION RESPIRATION. II. SURVIVAL OF THE DOG FOLLOWING A PROLONGED PERIOD OF RESPIRATORY ARREST

Abstract

Fifteen small dogs were anesthetized with pentothal Na. An injn. cannula was tied into a cephalic vein, a chest pneumograph was adjusted, and the animal was placed into a 5300 ml. chamber provided with windows. A mouth gag was used and the tongue was pulled forward to ensure patent airway. Twelve 1. of O2 were admitted into the chamber/min.; free exit for the gas from the chamber was also provided. The animals were allowed to breathe pure O2 for 15 mins. to accomplish partial denitrogenation, then respiratory arrest was produced and maintained for 45 mins. by the continuous intraven. infusion of 1% pentothal Na at suitable rates. The alveolar O2 and CO2 concns. were studied in 6 dogs at the end of the expt., before removal from the chamber, and in 4 dogs 3 mins. after removal from the chamber. Artificial respiration was started after the first sample of gas was taken, and another sample was obtained 30 mins. later. On resumption of spontaneous respiration, the dogs were given 150-200 ml. of 1/e M Ringer-lactate and V2-1 g.- of Na sulfadiazine intraven. Of the 15 dogs, 2 died after 35 and 43 mins., respectively, of respiratory arrest. Four of the remaining 13 dogs died within the next 44 hrs. The avg. alveolar O2 concn. in 6 dogs at the end of the expt., but before removal from the chamber, was 28.8% and the avg. alveolar CO2 concn. (8 expts.) was 43.0%. In 4 dogs, exposed to room air for 3 mins., the avg. alveolar O2 was 9.9%, and the avg. alveolar CO2 was 43.9%. The avg. heart rate during the respiratory arrest was between 114 and 127. The heart beat became stronger during the first 20 mins. of respiratory arrest, but became weaker in the last 15 mins. Cyanosis of the tongue, when encountered, appeared in the last 15 mins. Rectal temp. remained about 101 [degree]F while the animals were in the chamber. After 30 mins. of spontaneous or artificial respiration, the avg. rectal temp. was 99.0[degree]F, and after 60 mins. 96.4[degree]F. Recovery from anesthesia was slow but after 48 hrs., all the surviving dogs were able to stand. No permanent disturbances were observed in the 9 dogs that made complete recovery. The survival of the dogs is attributed to the fact that adequate oxygenation could be maintained through the action of the "Hb-O2 pump". The rise of the alveolar CO2 concn. to 43% is explained by the circumstance that no similar mechanism aids the outward diffusion of CO2. The high CO2 concn. undoubtedly exerted an additive anesthetic effect, and the dogs required little pentothal Na after 30 mins. of respiratory arrest. The expts. indicate that 30 mins. of diffusion respiration are relatively safe in dogs.