176 Procccdings Columbia Biochemical Association [Sept. 



artificial respiration, and to the production of shock in connection 

 with intrathoracic surgery. It has prompted us to investigate the 

 degree of acapnia and the associated shock produced by excessive 

 artificial respiration. 



We soon found that the diminution of carbon dioxide in the 

 blood in ordinary intrathoracic insufflation was neghgible. On the 

 other hand, it has been quite an easy matter for us to reduce the 

 amount of carbon dioxide in the blood to from one-third to one-half 

 the normal amount by forced rapid inflation and deflation of the 

 lungs. The artificial respiration was performed 45 to 90 times a 

 minute and was continued for periods varying from 30 minutes to 

 3 hours. These experiments have differed from those of Hender- 

 son in that the animals were allowed to recover. The trachea was 

 not divided but respiration was performed by inserting a large, 

 rather tightly fitting, tube through the larynx into the uninjured 

 respiratory tract. The blood pressures in our experiments were 

 not accurately measured, the animals being left as nearly normal as 

 possible after the Operations. The degree of shock was estimated 

 entirely from the condition of the animals after the Operation and 

 the manner in which they recovered from it. Judged in this manner 

 there was nothing about these animals to indicate a serious degree 

 of shock or any greater disturbance than could be accounted for. by 

 three other factors to which we desire to call attention in connection 

 with these experiments and which, unless guarded against, can alone 

 cause considerable depression and even death. 



( I ) In all experiments in which excessive artificial respiration 

 is employed there is a great reduction in the animal's body heat. 

 The temperature can easily fall to 85° F. (2) There is a very 

 evident possibility (which we believe to be a fact) that the rapid and 

 complete filling of the lungs exercises a definite interference with the 

 return of the blood to the heart. The fall of the blood pressure, as 

 estimated with the finger, and the rapidity of the heart's actioncoin- 

 cide closely with the pressures used to inflate the lungs; indeed, a 

 scarcely perceptible pulse may be immediately improved by slightly 

 lowering the latter pressures. (3) The duration of the apnea fol- 

 lowing these experiments depends as much upon the amount of mor- 

 phin and ether administered as upon any other factor. We do not 



