404 Relation of Acapnia to Shock [April 



In one experiment with an increase in intrabronchial pressure 

 of from 8 to 30 mm. Hg, the blood pressure feil from 122 to 55 

 mm. Hg, and the Volumetrie tracing indicated that the Output from 

 the heart had diminished about 44 per cent. These variations in 

 blood-pressure were completed within a few seconds after the 

 change in intrabronchial pressure, and could be duplicated 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 diminution of the venous return 

 to the heart, resulting from compression of the veins in the thorax. 

 In view of the marked changes in the blood-pressure and Output of 

 the heart resulting from small variations in intrapulmonic pressure, 

 it is evident that, in any experiments planned for the purpose of 

 estimating the part played in the production of shock by a diminu- 

 tion of carbon-dioxide content, induced by artificial hyper-respira- 

 tion, the effects of the increase of intrapulmonic pressure upon the 

 return flow of blood to the heart must be considered. 



With 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 seventy times per minute. 

 The animals were given morphin, and ether was administered only 

 when necessary. In these experiments, blood-pressure feil 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, the blood pressure increased 

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

 blood analysis showed that the carbon-dioxide content, at the end, 

 was only 40 to 50 per cent. of the original amount. These animals, 

 at the end of two to three hours of artificial respiration, were all 

 in a condition of deep shock. This degree of shock was indicated 

 by a rapid pulse, a low blood-pressure, and a marked degree of 

 insensibility to sensory Stimulation. Three of the animals so 

 treated lived three days (dying of secondary effects of the experi- 

 ment), and one lived twenty-four hours. None of them died from 

 the immediate effects of the experiment. During these experiments, 

 when the artificial respiration was interrupted or permanently 



