Comparison of two automatic blood pressure recorders and the mercury sphygomomanometer

The Physiometrics automatic blood pressure recorder was compared with the mercury sphygmomanometer in 2200 children aged 5-14 years, each reexamined after 3 and 5 years; the Physiometrics recorder produced higher intrachild correlations. In trials we could transfer what were essentially Physiometrics readings into levels similar to mercury sphygmomanometric readings by filtering out the infrasonic frequency band. The Physiometrics USM-105 was compared with its successor, the Physiometrics SR-2, on 378 children aged 10-17 years. The SR-2 measured lower than the USM-105: 4.1 mm Hg systolic and 8.5 mm Hg diastolic; differences were larger in the younger children. Both in mean levels and correlations, SR-2 readings were closer to the mercury sphygmomanometer's than were USM-105 readings, except or diastolic SR-2 readings, which were farther below the mercury sphygomomanometer 4th-phase readings than the USM-105. However, the SR-2 readings are likely closer to the true diastolic pressure in children 13 years and older, although we did not measure pressures intraarterially. Disc readings for systolic pressures showed coefficients of correlation averaging 0.96 among (n = 168) and 0.98 within (n = 40) readers for both models, but diastolic readings showed marked improvement form USM-105 (0.73, 0.81) to SR-2 (0.91, 0.97). In many of the parameters observed, SR-2 constitutes an improvement over USM-105. Automatic recorders offer certain advantages for measuring blood pressure in large-scale epidemiologic studies.