The relative accuracy of sequential same-arm and simultaneous opposite-arm measurements for the intra arterial validation of blood pressure monitors

Objective: To compare the results of simultaneous opposite-arm and sequential same-arm intra-arterial validation of automated blood pressure monitors. Design: Intra-arterial blood pressure measurements were compared with blood pressure measurements obtained using conventional sphygmomanometry and two automated blood pressure monitors (the Dinamap XL and the SpaceLabs Scout) using a methodology based on the protocol published by the Association for the Advancement of Medical Instrumentation (AAMI) for the intra-arterial validation of automated monitors. Methods: Thirteen women with radial arterial lines were recruited from the obstetric intensive care unit at Groote Schuur Hospital, Cape Town. For each woman, intra-aterial blood pressure measurements were compared with those obtained by mercury sphygmomanometry and by using the two automated blood pressure monitors with both a sequential same-arm protocol and a simultaneous opposite-arm protocol. The mean and SD of the differences was calculated for each protocol and the results were compared using Student's t test. Results: The differences between the 'means of the differences' for these two protocols never differed by more than 2 mmHg. For individuals the differences between data obtained using the two methodologies were up to 32 mmHg for mercury sphygmomanometry and 18 mmHg for the automated monitors. The differences between the SD of the differences were all less than 3 mmHg except for that of systolic blood pressure obtained by mercury sphygmomanometry, which was 7 mmHg. Conclusions: The results of this study show that a sequential same-arm and a simultaneous opposite-arm comparison of intra-arterial and indirect blood pressure measurements yield similar results.