THE CARDIAC OUTPUT IN MAN: STUDIES WITH THE LOW FREQUENCY, CRITICALLY-DAMPED BALLISTOCARDIOGRAPH, AND THE METHOD OF RIGHT ATRIAL CATHETERIZATION 1

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Abstract
The details of the construction of this ballistocardiograph are presented and the procedures for its adjustment to definite physical conditions described. The adjustments enable the reproduction of this type of ballistocardiograph to be made easily, and permit, without further calibration by the catheter method, the use of the stroke vol. equation tested in this study. Eighty-one detns. of the cardiac output by the method of right atrial catheterization and by almost simultaneous ballistic records with the ballistocardiograph described here have been made on a group of 08 normal subjects and hospital patients under a variety of conditions. Of the 54 detns. on subjects without heart disease, 87% of the ballistic values were within 25% of the catheter values. For 10 patients with aortic insufficiency, the ballistic values were generally much larger than the catheter values. For 17 other cardiac patients the ballistic values were within 25% of the catheter values in 60% of the cases. Serial measurements on patients in shock and during recovery showed a good correlation between the cardiac output measurements by the 2 methods. This observation suggests that changes in cardiac output in any individual subject may be measured with considerable accuracy by means of the low frequency, critically damped ballistocardiograph. It is concluded that this ballistocardiograph provides a useful and reasonably accurate method of determining cardiac output in normal subjects, and in patients with a variety of disease conditions.