Hand-free stethoscope--method and instrument for more reliable blood pressure measurements.

Measurement of blood pressure is subject to two sources of variation: biological and measurement variation. It is important to bear in mind that the ability to interpret the Korotkoff sounds correctly determines the levels of both systolic and diastolic blood pressure. To improve the ability to distinguish between the Korotkoff phases, the handfree stethoscope and the hand-free method were developed. The improved stethoscope head was fixed under the edge of the cuff, thus reducing the noise generated from physiological tremor and other movements. This resulted in more distinct Korotkoff sounds. Furthermore, the new method reduced the spreading of blood pressure values. In 107 patients the average systolic blood pressure recording was 3.1 mmHg higher and the average diastolic blood pressure was 3.5 mmHg lower. We conclude that the new stethoscope and technique provide a means of significantly improving the indirect measurement of blood pressure.