Increasing observer objectivity with audio-visual technology: the Sphygmocorder

The most fallible component of blood pressure measurement is the human observer. The traditional technique of measuring blood pressure does not allow the result of the measurement to be checked by independent observers, thereby leaving the method open to bias. In the Sphygmocorder, several components used to measure blood pressure have been combined innovatively with audio-visual recording technology to produce a system consisting of a mercury sphygmomanometer, an occluding cuff, an automatic inflation-deflation source, a stethoscope, a microphone capable of detecting Korotkoff sounds, a camcorder and a display screen. The accuracy of the Sphygmocorder against the trained human observer has been confirmed previously using the protocol of the British Hypertension Society and in this article the updated system incorporating a number of innovations is described.