58 



Scientific Proceedings (117). 



The oscillations of pressure elicited during rapid breathing by 

 the interference method we have designated as cardio-respiratory 

 interference waves. 



The most striking difference in the respiratory relations of the 

 simple and interference waves is that in the simple waves the 

 blood pressure changes are complete within the period of a single 

 respiration, while in the interference waves the gamut of the 

 blood pressure changes is run through in the interval of several 

 respirations. 



The production of interference waves of blood pressure is de- 

 pendent upon the establishment of cardio-respiratory cycles in 

 which the number of respirations is greater by one or lesser by 

 one than the number of heart beats making up the waves and 

 occurring in the same time interval. 



When these conditions are fulfilled we may conceive of the 

 heart beats as moving through respiration, the direction of the 

 movement being determined by the relative rates of the heart and 

 respiration, that is, whether the respiratory rate is slower or faster 

 than the heart rate. A cardio-respiratory cycle is complete when 

 two beats (the first and last of the interference wave) fall at ap- 

 proximately the same time in respiration. 



Whereas in the simple respiratory waves we found the highest 

 pressure to be associated with approximately the beginning of 

 inspiration, in the cardio-respiratory interference waves we found 

 the highest pressure to obtain at approximately the beginning of 

 expiration. 



Without definitely assigning the responsibility for the pro- 

 duction of interference waves to any particular respiratory factor, 

 we are inclined to favor the hypothesis that they are primarily 

 due to the changing intra-thoracic pressure accompanying respira- 

 tion. 



It is possible by breathing slightly slower or slightly faster 

 than half the heart rate to produce double interference waves of 

 blood pressure, that is, under these conditions, two waves of 

 blood pressure may be in progress simultaneously. Each of the 

 double waves is formed by alternate heart beats, one being made 

 up of the even numbered and the other of the odd numbered 

 beats. Double cardio-respiratory interference waves are to be 

 explained in the same manner as the single waves. 



