Abstract
Using a modified heart-lung preparation of Starling, with the arterial cannula inserted in the brachial cephalic artery in the first experiments, and in the later experiments in the arch of the aorta, the following experiments were done.
In drawing conclusions as to the external work of the heart, we consider that our experiments establish the diastolic volume of the heart as an index of the energy consumption of the heart and therefore a measure of the work of the heart, provided the heart muscle function remains as constant throughout the period under consideration. Only one experiment is given here.
Calibration of elastic coefficient in terms of percentage volume increase of arterial system to mm. Hg. increase pressure or mm. Hg. increase in pressure/% increase in volume. This is the “effective” elastic coefficient or rigidity of arterial system.
Without Air Chamber or Arteriosclerosis. Content of “effective” arterial system = 210 cc. 2 cc. blood injected into system gives a rise of 56 mm. Hg. in pressure.
2/210 = 0.95% increase in volume for 56 mm. Hg., or 1% increase in volume for 59 mm. Hg. A. V. Hills normal artery between 80-120 mm. Hg. showed 6.6% increase in volume for 40 mm. Hg., or 1% increase in volume for 6 mm. Hg. Ergo in this system without air chambers and representing extremely severe arteriosclerosis, there is a rigidity 9.8 × normal “mean” artery of A. V. Hill at normal pressure.
With Air Chamber or Normal. Content of arterial system = 240 cc. 20 cc. blood injected into system gives a rise of 27 mm. Hg. 20/240 = 8.3% for 27 mm. Hg., or 1% increase for 3.3 mm. Hg. Ergo rigidity is 1/2 that of A. V. Hill “mean” normal artery.
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