A New Noninvasive Blood Pressure Recorder Employing a Liquid-Filled Cuff.

The systolic and diastolic blood pressures (BP) measured by the conventional auscultatory method tend to be lower and higher respectively than the corresponding values obtained with invasive direct measurement. This study aims to develop a new, noninvasive device employing a liquid-filled cuff to mea sure BP accurately. The new BP recorder employs hydraulic pressure instead of air pressure in a double cuff (outer cuff and inner cuff with an implanted pressure transducer) surrounding the upper arm. The basic principle of this method is based on evidence that the pulsatile pattern of the pressure tracings obtained changes when the inner-cuff pressure reaches diastolic BP and changes again when it exceeds systolic BP. BP values measured directly from the brachial artery were compared with those obtained simultaneously by the conventional auscultatory method or by our new method in 7 normotensives and 14 hypertensive patients. The differnce in systolic BP between the auscultatory and direct methods was -6.8±4.0 (SD) mmHg and the diastolic BP difference was 1.1±6.5mmHg. In contrast, the systolic BP difference between the new method and the direct method was -0.6±2.0mmHg and that for diastolic BP was 0.6±1.9mmHg. These values were significantly smaller than the differences obtained with the auscultatory method (p<0.05). Improved conduction of brachial artery pulsation through the liquid-filled cuff to the transducer apparently improved the analysis of arterial pulsation. This new device employing a liquid-filled cuff could be useful for assessing hypertension. (Hypertens Res 1992; 15: 163-169)