Blood pressure differences between a mercury sphygmomanometer and two automatic devices

Purpose Blood pressure (BP) is one of the most important pieces of information to diagnose cardiovascular diseases but the measurement readings could be easily changed by various factors. If these readings are wrong, it may ultimately lead to a misdiagnosis. In addition, there is a problem when there are different devices used to read blood pressure because these devices may give different readings. Methods Four different BP measurement devices were used, including two mercury sphygmomanometers and two automatic digital devices. Thirty-eight healthy young people (mean age = 27.1±6.1 years) stayed one night at a clinical center and the BPs were measured from their right arms on the following day. Factors such as exercise, food, and smoking that may affect the BP were controlled and prohibited. All tests were repeated three times and all devices were calibrated before the test. Absolute BP value difference between a mercury sphygmomanometer and an automatic digital device was counted for the BP difference between devices ≥ 5 mmHg and ≥ 10 mmHg of each measurement. Results Significant inter-device BP differences were found between a mercury sphygmomanometer and two automatic devices (p<0.01) while no significant difference was found between mercury sphygmomanometers (p>0.5); all subjects showed BP difference less than 5 mmHg between two mercury sphygmomanometers while only 32% and 38% of subjects showed BP difference less than 5 mmHg for two out of three repeated tests between a mercury sphygmomanometer and an automatic device, and even 26% ~ 36% of subjects showed BP difference ≥ 10 mmHg. Conclusions This study result stresses that it is necessary to check the reliability of automatic blood pressure devices used in the hospitals. In addition, an easier and more convenient protocol should be developed for the routine calibration of automatic devices.