A new audiovisual technique for recording blood pressure in research: the Sphygmocorder

OBJECTIVETo devise a method of blood pressure measurement capable of being substituted for the fallible human observer in validation of blood pressure measuring devices. DESIGNA number of components used to measure blood pressure have been combined innovatively with audiovisual recording technology to produce a system, named the Sphygmocorder, which consists of a mercury sphygmomanometer, an occluding cuff, an inflation source, a stethoscope, a microphone capable of detecting Korotkoff sounds, a camcorder and a display screen. METHODSTo determine the accuracy of the Sphygmocorder against the trained human observer, the Sphygmocorder has been validated in three separate studies in which three devices for self-measurement of blood pressure, the Omron HEM-705CP, the Phillips HP5332 and the Nissei DS-175, were being validated against two trained observers in 85 subjects with a wide range of blood pressure according to the protocol of the British Hypertension Society. RESULTSThe Sphygmocorder was as accurate as at least one of the observers in each of the validation studies and therefore allows replacement of trained observers by the new device. CONCLUSIONThe Sphygmocorder, which retains the time-honoured technique of blood pressure measurement with a mercury sphygmomanometer and an auscultating observer, and provides, in addition, objective evidence of the measurement recorded, which can be stored and re-examined, can be used as a substitute for human observers in validation studies of blood pressure-measuring devices.