From the Guidelines
Blood pressure measurements taken with an adult cuff below the elbow are typically higher than those taken above the elbow, which is the standard location. The upper arm (brachial artery) measurement is considered the gold standard for clinical decision-making. When blood pressure is measured at the forearm, systolic readings can be higher and diastolic readings can also be higher compared to upper arm readings. This difference occurs because arteries become narrower and more resistant as they move away from the heart, creating higher pressure readings in more distal locations, as noted in the recommendations for blood pressure measurement in humans by the American Heart Association Council on High Blood Pressure Research 1.
Key Points to Consider
- The standard location for blood pressure measurement is the upper arm, with the stethoscope at the elbow crease over the brachial artery.
- Monitors that measure pressure at the wrist and fingers have become popular, but it is essential to realize that the systolic and diastolic pressures vary substantially in different parts of the arterial tree.
- In general, the systolic pressure increases in more distal arteries, whereas the diastolic pressure decreases, as stated in the guidelines for blood pressure measurement 1.
- For accurate blood pressure assessment, the cuff should be placed on the upper arm with the lower edge about 1 inch above the antecubital fossa (elbow crease), with the patient seated, back supported, feet flat on the floor, and arm supported at heart level.
- If upper arm measurement is impossible due to size, injury, or other factors, forearm measurements can be used but should be interpreted with the understanding that they likely overestimate true blood pressure, based on the principles outlined in the American Heart Association's recommendations 1.
Clinical Implications
The clinical implications of these findings are significant, as accurate blood pressure measurement is crucial for diagnosing and managing hypertension. Using the upper arm for blood pressure measurement is recommended to ensure accurate readings and to minimize the risk of overestimating or underestimating blood pressure. By following the guidelines for blood pressure measurement, healthcare professionals can provide high-quality care and improve patient outcomes, as emphasized in the statement for professionals from the Subcommittee of Professional and Public Education of the American Heart Association Council on High Blood Pressure Research 1.
From the Research
Blood Pressure Comparison
- The comparison of blood pressure measurements between the upper arm and forearm has been studied in various research papers 2, 3, 4, 5, 6.
- The studies suggest that blood pressure measurements in the forearm tend to be higher than those in the upper arm, with mean differences ranging from 2.2 mmHg to 4.0 mmHg for systolic blood pressure and 2.3 mmHg to 3.4 mmHg for diastolic blood pressure 3, 4, 6.
- However, the differences between forearm and upper arm blood pressure measurements can vary widely, with 95% limits of agreement ranging from ±13.7 mmHg to ±19 mmHg for systolic blood pressure and ±14.4 mmHg for diastolic blood pressure 3.
- The studies also suggest that the agreement between forearm and upper arm blood pressure measurements can be affected by factors such as age, sex, ethnicity, smoking history, and obesity, although the evidence is not consistent across all studies 3, 4.
- Overall, the research suggests that forearm blood pressure measurements cannot be used as a direct substitute for upper arm measurements, but may be useful in certain situations where upper arm measurement is not feasible 2, 3, 5, 6.
Key Findings
- Forearm systolic blood pressure tends to be higher than upper arm systolic blood pressure, with a mean difference of 2.2 mmHg to 4.0 mmHg 3, 4, 6.
- Forearm diastolic blood pressure tends to be higher than upper arm diastolic blood pressure, with a mean difference of 2.3 mmHg to 3.4 mmHg 3, 4, 6.
- The differences between forearm and upper arm blood pressure measurements can be significant, with p-values ranging from 0.002 to <0.001 3, 4, 6.
- The use of forearm blood pressure measurements may be justified in certain situations, such as when upper arm measurement is not feasible, but should be interpreted with caution due to the potential for variability 2, 3, 5, 6.