Should the arm be elevated to take blood pressure?

Blood Pressure Measurement: Arm Position

No, the arm should NOT be elevated above heart level to take blood pressure—this will produce falsely low readings. The arm must be positioned precisely at the level of the right atrium (mid-sternum or fourth intercostal space when sitting) to obtain accurate measurements 1.

Critical Positioning Requirements

The arm must be supported at heart level, not elevated above or hanging below it. Deviations from heart level cause clinically significant errors due to hydrostatic pressure effects 1:

• Arm above heart level: Readings will be falsely LOW by approximately 2 mmHg for every inch above heart level, potentially 10 mmHg or more total 1
• Arm below heart level: Readings will be falsely HIGH by the same magnitude 1
• These hydrostatic effects are consistent across all adult ages and both sexes 2

Proper Measurement Technique

Sitting Position (Most Common)

• Position the arm at the midpoint of the sternum or fourth intercostal space (right atrium level) 1
• Support the arm on a desk or armrest at this level—do not have the patient hold their arm up 1
• Back must be supported against a chair (not an examination table) to avoid falsely elevated diastolic pressure by 6 mmHg 1
• Feet flat on floor with legs uncrossed (crossing legs raises systolic BP by 2-8 mmHg) 1

Supine Position

• The right atrium is approximately halfway between the bed and the sternum when lying down 1
• Support the arm with a pillow to elevate it to this level—do not let it rest flat on the bed 1
• Arm resting on the bed will be below heart level and produce falsely elevated readings 1, 3

Magnitude of Errors from Improper Positioning

Research demonstrates substantial clinical impact from positioning errors 4, 3, 2, 5:

• Arm on chair support vs. heart level: Systolic BP overestimated by 9.3 mmHg, diastolic by 9.4 mmHg 5
• Arm on desk vs. heart level: Systolic BP overestimated by 6.1 mmHg, diastolic by 5.7 mmHg 5
• Arm parallel to body (hanging) vs. elevated to heart level: Systolic BP overestimated by 8-9 mmHg, diastolic by 12-14 mmHg 2
• Supine with arm on bed vs. arm at right atrium level: Systolic BP overestimated by 4.6 mmHg, diastolic by 3.9 mmHg 3

Additional Critical Considerations

Muscle Tension Effect

If the patient holds their arm up unsupported (rather than having it supported by the examiner or furniture), isometric exercise will falsely elevate the pressure 1. Always ensure proper arm support.

Body Position Differences

When arm position is meticulously controlled at right atrium level in both positions 3:

• Supine systolic BP is approximately 8-10 mmHg HIGHER than sitting 1, 3
• Supine diastolic BP is approximately 5 mmHg LOWER than sitting 1

Orthostatic Hypotension Assessment

Arm position must remain constant (at heart level) when measuring both supine/sitting and standing blood pressures 6. Changing arm position between measurements (e.g., parallel when supine, perpendicular when standing) significantly overestimates orthostatic changes and can lead to false-positive diagnoses 6.

Common Pitfalls to Avoid

• Never measure with the arm hanging down at the patient's side—this produces falsely elevated readings 1
• Never elevate the arm above heart level—this produces falsely low readings 1
• Never allow unsupported arm positioning—muscle tension from holding the arm up elevates BP 1
• Never assume sitting and supine readings are equivalent—they differ significantly even with proper arm positioning 4, 3
• Always use the 2024 ESC guideline approach: measure BP in both arms at first visit, and if difference >10 mmHg, use the arm with higher readings for subsequent measurements 1