Measuring Blood Pressure
|Effects of body position on blood pressure
Blood pressure is commonly measured in the seated or supine position; however, the two positions give different measurement values. With that in mind, any time a value is recorded, body position should also be recorded. It is widely accepted that diastolic pressures while sitting are higher than when a patient is supine by as much as 5 mmHg. When the arm is at the level of the heart, systolic pressure can be 8 mmHg higher, such as when a patient is in the supine position rather than sitting. A patient supporting their own arm (isometric exercise) may increase the pressure readings. If the patient’s back is not supported (i.e., when a patient is seated on an exam table instead of a chair) the diastolic pressure may be increased by 6 mmHg. Crossing the legs also may raise systolic pressure by 2-8 mmHg. Arm position plays a dramatic role in value errors as well. If the arm is below the level of the heart, values will be too high; if the arm is above the level of the heart, values will be underestimated. For every inch the arm is above or below the level of the heart, a 2 mmHg difference will be found (Pickering et al. Circ 2005;111:697-716).
Differences in bilateral measurements
|Section: Measuring Blood Pressure||
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