Lack of comparability of two automated blood pressure monitors in a hypertensive population.

Two frequently used automated, blood pressure monitors, the Arteriosonde and the Dinamap, were compared with each other and with a standard mercury sphygmomanometer. Fifteen patients with elevated blood pressure were studied: 5 were untreated, 5 received a diuretic alone, and 5 received a beta blocker alone. One hundred and twenty blood pressure measurements were taken from each subject with two different instruments (one on each arm) in a 2 (supine or standing position) X 2 (left or right arm) X 3 (three different sets of pairwise instrument comparisons) X 5 (five one-minute interval measurements per phase) factorial design. A reasonable inter-instrument comparability for systolic blood pressure was found with mean deviations of +1.3 mmHg and -3.8 mmHg from the mercury sphygmomanometer for the Dinamap and Arteriosonde, respectively. Differences between instruments for diastolic pressure however, were significantly larger. The Arteriosonde systematically obtained higher diastolic pressure values (+7.4 mmHg) than the mercury sphygmomanometer or the Dinamap (10.7 mmHg). Diastolic pressure on the Dinamap was on average 5.2 mmHg lower than on the mercury sphygmomanometer. Left/right arm differences and differences for the treatment conditions were not observed. Findings clearly suggest that these two automated blood pressure monitors cannot be used interchangeably with each other or with the mercury sphygmomanometer in either a research or clinical setting. Overall the Dinamap approached mercury sphygmomanometer measures more closely than did the Arteriosonde.