Observing the brachial artery through a pressure cuff

A technique is described which enables ultrasonic imaging of the brachial artery whilst pressure is applied via a pressure cuff. This involves a new instrument-a sphygmomanometer, which uses water as opposed to air as the pressure medium, in order to permit ultrasonic imaging through the cuff. The technique was found to be acceptable in the clinical setting, and gave a measurement of the systolic blood pressure which correlated with the conventional cuff measurement in eleven elderly subjects (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.