Comparison of the effects of arm position and support on blood pressure in hypertensive and normotensive subjects.

One hundred and twenty-three hypertensive patients were compared with 120 normotensive subjects, to study the effect of arm position and arm support on blood pressure (BP). The BP tended to increase from the sitting to the standing position in both groups, except when subjects were standing with the arm held out perpendicular to the body, in which case the BP decreased. The lowest standing recordings were observed when the elbow was slightly flexed and supported at this position. The highest BP was observed in the standing position with the arm hanging at the side. Differences in the systolic BP between those with the arm hanging and when it was perpendicular to the torso, or flexed and supported at the elbow were 7.45 mmHg in hypertensives (p = 0.002) and 16.35 mmHg in normotensives (p < 0.0001). Similar figures for diastolic BP were 7.84 mmHg for hypertensives (p < 0.0001) and 9.81 mmHg for normotensives (p < 0.0001). Failure to support the arm at the elbow, even when it was positioned perpendicularly to the torso, led to an increase of 4.87/4.81 mmHg in hypertensives and 7.61/2.83 mmHg in normotensives. Arm position and arm support affect the accuracy of BP measurements. The effect of arm position is more than that of arm support, although they are additive, and more in normotensives. Healthcare providers should adhere to recommended guidelines for BP measurement.