Evaluation of two devices for self-measurement of blood pressure according to the international protocol: the Omron M5-I and the Omron 705IT

BACKGROUND: Two devices for self-measurement of blood pressure at the brachial artery-the Omron M5-I and the Omron 705IT-were evaluated according to the international protocol of the European Society of Hypertension. DESIGN: The international validation protocol is divided into two phases: the first phase is performed on 15 selected subjects and if the device passes this phase, 18 supplementary subjects are included making a total number of 33 subjects on which the final validation is performed. METHODS: For each subject, four blood pressure (BP) measurements were performed simultaneously by two trained observers using mercury sphygmomanometers alternately with three measurements by the tested device. The difference between the BP value given by the device and that obtained by the two observers (mean of the two observers) was calculated for each measure. The 99 differences were classified into categories (<or=5, <or=10, <or=15 mmHg). The number of differences in each category was compared to the number required by the international protocol. An individual analysis was then done to determine for each subject the number of comparisons <or=5 mmHg. At least 22 of the 33 subjects should have two of their three comparisons <or=5 mmHg. RESULTS: The two tested devices passed the first phase of the validation process. For the second phase, the average differences between the device and mercury sphygmomanometer readings were -0.9+/-5.8 and -0.8+/-4.8 mmHg for systolic blood pressure (SBP) and diastolic blood pressure (DBP) respectively for the Omron M5-I device and -0.2+/-4.5 and -2.0+/-4.8 mmHg for the Omron 705IT device. Readings for the two devices differing by less than 5, 10 and 15 mmHg for systolic and diastolic values fulfil the recommendation criteria of the international protocol as well as the individual analysis. CONCLUSIONS: The Omron M-5I and the Omron 705IT devices pass the validation recommendations of the international protocol.