Are automated blood pressure monitors accurate enough to calculate the ankle brachial pressure index?

Objective: Conventional sphygmomanometers are being replaced by automated devices; can they be used to accurately calculate ABPI?

Method: Thirty-six volunteers (72 legs) attending a vascular clinic had their ankle, brachial blood pressure and ABPIs calculated using each of these 3 methods. (1) Conventional aneuroid BP cuff with hand held doppler. (2) OMRON HEM 705CP portable automated BP monitor. (3) The hand held doppler to determine systolic BP measured by the OMRON.

Results: Conventional doppler readings for brachial and ankle pressures were generally higher than those obtained digitally by less than 3 mmHg but this was not statistically significant. This did not translate into a significant difference in ABPIs obtained using all 3 techniques; the correlation coefficient of conventional ABPI with automated ABPI (method 2) was 0.746, this was improved to 0.899 using method 3. The OMRON failed to detect a signal in 16 of the 72 legs, 11 of these legs had ABPIs <0.66.

Conclusion: Conventional doppler measurements give higher readings for systolic blood pressure but there is no significant difference when calculating ABPI. A normal digital ABPI excludes significant vascular disease and a low digital ABPI indicates disease. If no blood pressure is recordable a doppler should be used to confirm the true result. Automated oscillometric BP monitors may be used to accurately measure ABPI in non-diabetics in the community without teaching clinicians to use a doppler, thus removing observer error. This may be of particular use in the community to exclude significant arterial disease in venous ulcer patients and assess general cardiovascular risk.