132 



Scientific Proceedings (53). 



In one experiment, with an increase of intrabronchial pressure 

 from 8 mm. to 30 mm. Hg, blood pressure fell from 122 mm. to 

 55 mm. Hg and the volumetric tracing indicated that the output 

 from the heart had diminished about 44 per cent. These varia- 

 tions in blood pressure were completed within a few seconds 

 after the change in intrabronchial pressure, and could be dupli- 

 cated at will. 



A rise of intrabronchial pressure above 8 to 10 mm. Hg always 

 caused a fall in blood pressure, and it was concluded that the varia- 

 tion in pressure was the result of a diminished venous return to 

 the heart, resulting from compression of both the pulmonary and 

 systemic veins in the thorax. 



In view of the marked changes in heart output and blood 

 pressure resulting from small variations in intrapulmonic pressure, 

 it is evident that, in any experiments attempting to estimate the 

 part played in the production of shock by a diminution of C0 2 

 which is caused by hyperartificial respiration, the effect of the 

 increase of intrapulmonic pressure upon the return flow of blood 

 to the heart must be considered. 



In the second series of animals, Henderson's experiments were 

 duplicated, the dogs being artificially respired by means of a force 

 and suction pump, working about 70 times per minute. The 

 animals were given morphine, and ether was administered only 

 when necessary. In these experiments, blood pressure fell about 

 40 per cent, within one minute after artificial respiration was begun, 

 and then decreased more slowly throughout the experiment to 

 between 40 and 50 mm. Hg. At the end of the experiment when 

 the artificial respiration was stopped, blood pressure increased 60 

 to 90 per cent, within a few seconds. In all experiments the blood 

 gas analysis showed the C0 2 content at the end to be only 40 to 

 50 per cent, of the original volume. These animals, at the end of 

 2 to 3 hours of artificial respiration, were all in a condition of deep 

 shock. This degree of shock was indicated by a rapid pulse, a 

 marked degree of coma, and insensibility to a sensory stimulation. 

 Three of the animals so treated lived three days (dying of sec- 

 ondary effects of the experiment), and one lived 24 hours. None 

 of them died from the immediate effects of the experiment. 

 During these experiments when the artificial respiration was 



