THE CIRCULATION IN MAN IN THE HEAD-DOWN POSITION, AND A METHOD FOR MEASURING THE VENOUS RETURN TO THE HEART

¹ From the Physiological Laboratory of the Yale Medical School

In the inverted or head down position (30 to 45 degrees) the heart rate in 10 men was slower than in the flat position by an average of 9.5 beats a minute (maximum 23, minimum, 4.5), and slower than in the erect position by 17 (maximum 34, minimum 10). The diastolic distending force of venous pressure was increased but arterial pulse pressure was not augmented. This fact we interpret in support of the view that normally in the erect position the distending force of venous pressure is above the critical value, and the heart works therefore at maximum efficiency for the rate of beat.

No third heart sound was audible in the inverted position.

The conditions and significance of venous pressure measurements are discussed. The necessity of recognizing some sort of veno-pressor mechanism regulating the venous return to the heart is pointed out. A method of estimating the efficiency of the vensus return is described. By this method it is found that a very distinct decrease in the volume of the venous return is generally induced in man by anesthesia and operation, and occurs also in acute disease.

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