Simultaneous Direct and Indirect Blood Pressure Determinations.

Abstract

In experiments on dogs, Erlanger found that the direct blood pressure in the femoral artery was but slightly higher than the indirect pressure. Kolls and Allen found very little difference between the results of cannulation and the auscultatory method of blood pressure determination on both normal unanesthetized and etherized dogs. Rühl found the direct carotid pressure in rabbits to be fairly comparable to the bleeding time of the vessels of the leg. The following experiments are reported because of the marked variation found between direct and indirect blood pressure determinations. Etherized dogs varying in weight from 6.6 to 29.4 kgm. were used. Direct blood pressure readings were obtained from both left carotid and left femoral arteries, which were connected with mercury manometers and a kymograph. A sphygmomanometer cuff and stethoscope bell were used on the left hind leg to determine the auscultatory indirect blood pressure. In 14 experiments the indirect readings were from 20 to 100 mm. of mercury higher than the direct. Observations of the beginning flow of blood from the femoral artery during gradual deflation of the cuff were recorded. Bleeding occurred at a pressure below but much nearer the indirect than the direct. Thus there was a transmission of sound through the artery after the disappearance of bleeding. When shock was produced by intermittent bleeding from the carotid artery, the indirect pressure readings tended to more nearly approximate the direct readings.