ON THE CAUSE OF THE RESPIRATORY VARIATION OF THE BALLISTOCARDIOGRAM, WITH A NOTE ON SINUS ARRHYTHMIA

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Abstract
The genesis of the respiratory variation of the ballistocardiograms has been studied in several types of expts. Placing the subject on the table sc that the axis of his heart in expiration was in the line of the recording failed to reverse the normal respiratory variation. In a patient in the decerebrate condition, and also in normal persons, artificial respiration with an air blast did reverse the normal respiratory variation. Hence, this variation is due to changes of cardiac filling and not to changes in the position of the heart. Records obtained on a patient with a cardiac aneurysm permitted a qualitative estimate of the changes in output of each side of the heart during the respiratory cycle. Further information of this kind was obtained by simultaneous records of blood pressure and ballistocardiograms in a series of healthy persons. The results support a familiar physiologic conception as explanation for the respiratory variation of the ballistocardiogram. On inspiration, the filling, and so the output of the right heart, increases immediately, but the left heart''s output does not increase until an interval of several secs. has elapsed. On expiration, the right heart output diminishes immediately, to be followed after an interval by similar diminution of the left heart''s output. The change in the right heart''s output during the respiratory cycle is larger than that of the left. In the common respiratory arrhythmia of young adults, sinus arrhythmia, the slowing always occurs during expiration. Under artificial respiration with blasts of air, the slowing may occur during inspiration, but in all records the slowing occurs when the ballistic impacts are either small or about to diminish. Therefore, evidence supports the well-known conception that this arrhythmia is due to changes in cardiac filling. It cannot be attributed to reflexes from the distention of the lungs or to phasic discharges from the respiratory center.