Blood pressure measurements in the ankle are not equivalent to blood pressure measurements in the arm
Date
2014-12
Authors
Goldstein, L.N.
Wells, M.
Sliwa, K.
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Background. Blood pressure (BP) is often measured on the ankle in the emergency department (ED), but this has never been shown to be
an acceptable alternative to measurements performed on the arm.
Objective. To establish whether the differences between arm and ankle non-invasive BP measurements were clinically relevant (i.e. a
difference of ≥10 mmHg).
Methods. This was a prospective cross-sectional study in an urban ED making use of a convenience sample of 201 patients (18 - 50 years of age) who were not in need of emergency medical treatment. BP was measured in the supine position on both arms and ankles with the correct size cuff according to the manufacturer’s guidelines. The arm and ankle BP measurements were compared.
Results. There was a clinically and statistically significant difference between arm and ankle systolic BP (SBP) and mean arterial pressure (MAP) (–13 mmHg, 95% confidence interval (CI) –28 - 1 mmHg and –5 mmHg, 95% CI –13 - 4 mmHg, respectively), with less difference in diastolic BP (DBP) (2 mmHg, 95% CI –7 - 10 mmHg). Only 37% of SBP measurements and 83% of MAP measurements were within an error range of 10 mmHg, while 95% of DBP measurements agreed within 10 mmHg. While the average differences (or the bias) were generally not large, large variations in individual patients (indicating poor precision) made the prediction of arm BP from ankle measurements unreliable.
Conclusion. Ankle BP cannot be used as a substitute for arm BP in the ED.
Description
Keywords
Blood Pressure, Blood Pressure Determination, Ankle blood pressure measurements, Arm blood pressure measurements
Citation
Goldstein, L.N., Wells, M., Sliwa, K. 2014. Blood pressure measurements in the ankle are not equivalent to blood pressure measurements in the arm. SAMJ;104(12):869-873