Accuracy of your blood pressure readings depends on how you hold your arm while measuring blood pressure. According to a US study published in JAMA Internal Medicine, certain arm positions can significantly overestimate test results and may lead to a misdiagnosis of hypertension.
For the study, researchers examined the effects of three different arm positions on 133 adults, 18 to 80 years old: an arm supported on a desk, supported on a lap and hanging at the patient's side. Participants had their blood pressure taken three times in each position and a fourth set of measurements with their arm supported on a desk.
Supporting the arm on the lap overestimated systolic blood pressure by 3.9 mmHg and diastolic blood pressure by 4.0 mmHg. An unsupported arm hanging at the side overestimated systolic blood pressure by 6.5 mmHg and diastolic by 4.4 mmHg.
The American Heart Association guidelines for BP measurement recommend using appropriate cuff size, sitting with your back straight (on a chair and not a sofa) and your feet flat on the floor with legs uncrossed. The middle of the cuff must be positioned at mid-heart level on an arm supported on a desk or table. But often in clinical settings, BP is measured with patients seated on an exam table without any, or inadequate, arm support, researchers said.
Proper guidelines should be followed both in the clinical setting and when measuring BP at home, the study concluded.