I’ve heard that there can be differences in blood pressure measurements taken depending on how a patient is positioned. How relevant is patient positioning to accurate blood pressure measurement?

It is very important. In general, a patient should be seated comfortably with their back and arm supported. Patients should sit with their feet flat on the floor and their legs uncrossed. When patients are supine, blood pressure measurements can vary 5-8 mmHg and this variation can increase if the arm is not supported to ensure that the cuff is at heart level. Similar variations can occur if the patient’s back or arm is unsupported, or if they are not seated correctly.