A comparison of direct and indirect blood-pressure determinations.

In this study a comparison between direct and indirect methods of obtaining blood pressure has been made. A statistical analysis of the data supports the view that the muffling of sounds, or the fourth phase of Korotkow, bears a closer and more constant relationship to diastolic pressure measured directly. This report, therefore, recommends the acceptance of muffling of the sounds of Korotkow as the measure of diastolic pIessure. IN January 1952, the Ontario Heart Foundation circulated a report of the American Heart Association, "Recommendations for the Determination of Blood pressure" and re(luested comments and criticism as to whether these recommendations should be accepted for distribution to Ontario physicians. The recommendations of the American Heart Association,' contain the following paragraph: "While some difficulties still exist in making absolute comparisons between pressures determined by optical manometers and those revealed by auscultatory criteria, a limited number of such comparisons strongly suggests that, on the average, the cessation of sounds conforms rather better to the intra-arterial diastolic pressure, and that dulling of sounds appears 5 to 10 mm. Hg above this level." In view of the fact that the above statement would favor a departure from what has been widely accepted clinical practice for many years, it was felt that further observations should be made so that any recommendations made by us would not be just an opinion reply, but based on experimental data. In the first part of this report a statistical analysis of the results of blood-pressure determinations both intra-arterially, and indirectly, on 50 patients, was therefore undertaken, with the further objective of comparing the relative merits of two commercially available recording instruments; one, a so-called "strain gauge" manometer, the other an instrument employing a condenser microphone principle (electro-manometer). In the second portion, a study of indirect pressure recordings on 15 young normal individuals under varying physiologic condi-tioins was carried out. PART I Method In this stu(ly observations were made on one arterial segment, the right brachial in each case, in the following manner: The patient was l)laced in the recumbent position on a hospital bed which allowed him complete comfort and relaxation. The cuff of a commercial sphygmomanomieter was placed around the patient's right arm (which rested on pillows at an oblique angle to his body), as close to the axilla as possible. The arm was then adjusted to a position constant for each patient, 5.0 cmii. measured in a vertical …