Abstract
The effects of rapid breathing were compared with those of more normal breathing upon the systolic blood pressure in man. Supplementary data were also obtained on the dog and cat.
For the well-known changes of blood pressure that occur during a single respiration, and which are more or less synchronous with the changing respiratory phases, we have proposed the name of simple cardio-respiratory waves to distinguish them from those waves produced by rapid breathing.
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 dependent 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 approximately 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.
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