In patients with obesity the distribution of subcutaneous tissue can make blood pressure measurement on the standard location of the upper arm difficult. In these cases, alternative locations such as the lower arm or wrist are commonly used. It is unknown if there is a discrepancy between these measurements for pregnant patients at extremes of body mass index.
We hypothesize that non-invasive blood pressure measurements on the lower arm and wrist will differ from the upper arm and that this difference will be greater with increasing body mass index.
We conducted a prospective observational study of pregnant patients from July to August 2020. We collected study subjects’ biometric measurements and took three blood pressure measurements (systolic and diastolic blood pressure) from the upper arm, lower arm, and wrist. Measurements at the lower arm and wrist were considered alternative locations and compared to the upper arm. We stratified patients by body mass index. Agreement between locations was assessed using a Bland-Altman analysis. We used linear regression to assess the blood pressure discrepancy dependence on body mass index.
We included 100 patients with 20 from each body mass index class. Blood pressure measurements at each site correlated but were discrepant. For the lower arm, there was an upward bias of 11.5 mmHg (limit of agreement: +30.7 to -7.8) for systolic blood pressure and 11.2 mmHg (limit of agreement:+25.9 to -2.9) for diastolic blood pressure as compared to the upper arm. For the wrist, there was an upward bias of 7.1 mmHg (limit of agreement: +35.1 to -20.9) for systolic blood pressure and 7.3 mmHg (limit of agreement:+26.2 to -11.7) for diastolic blood pressure as compared to the upper arm. Overall, there was a greater discrepancy in blood pressure measurements between the lower and upper arm with increasing body mass index. When comparing the lower arm to the upper arm, the discrepancy of systolic blood pressure increased by 0.43 mmHg (p<0.001) and diastolic blood pressure increased by 0.18 mmHg (p=0.02) with each increasing body mass index unit. There was no statistically significant change in the discrepancy of systolic (p = 0.45) or diastolic blood pressure (p = 0.86) in the upper arm versus the wrist measurements based on body mass index.
This study highlights that blood pressure measurements are higher when taken at alternative locations, such as the lower arm and wrist, and that lower arm blood pressure measurements are increasingly discrepant from upper arm measurements with increasing body mass index.

Copyright © 2021. Published by Elsevier Inc.

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