A technique is described which enables ultrasonic imaging of the brach
ial artery whilst pressure is applied via a pressure cuff. This involv
es a new instrument-a sphygmomanometer, which uses water as opposed to
air as the pressure medium, in order to permit ultrasonic imaging thr
ough the cuff. The technique was found to be acceptable in the clinica
l setting, and gave a measurement of the systolic blood pressure which
correlated with the conventional cuff measurement in eleven elderly s
ubjects (r = 0.89, p < 0.001). The technique should have an important
role to play in studying the origin of differences which occur between
direct and indirect blood pressure measurements.