From the Guidelines
The left arm is not necessarily the preferred site for measuring blood pressure (BP) due to its proximity to the heart.
Key Points
- Measuring BP in both arms is recommended at the first visit to detect any inter-arm difference 1.
- If a between-arm difference of >10 mmHg in systolic BP is recorded, subsequent BP readings should use the arm with the higher BP reading 1.
- The choice of arm for BP measurement is based on the presence of any inter-arm difference, rather than the proximity to the heart 1.
- Standardized measurement techniques, including the use of a validated and calibrated device, correct cuff size, and proper patient positioning, are essential for accurate BP measurement 1.
- Repeated measurements should be taken at intervals of at least 1 minute, and the average of those readings should be used to represent the patient's BP 1.
From the Research
Blood Pressure Measurement
- The left arm is not necessarily the preferred site for measuring blood pressure (BP) due to its proximity to the heart 2.
- Guidelines for the management of hypertension recommend that BP should be measured twice at every visit, in both arms at the first visit, and the right arm BP or higher BP should be recorded 2.
- Manufacturers of home BP monitors tend to design the device for measurement of left arm BP, but the arm preferred for BP measurement differs according to the methods recommended by the society and according to the home BP monitors 2.
Interarm Blood Pressure Differences
- Studies have shown that there are significant differences in blood pressure measurements between the left and right arms 3, 4.
- The prevalence of clinically important inter-arm blood pressure differences is substantial, with 5.8% of participants having a systolic difference between 10 and 15 mmHg, and 2.2% having a systolic difference of 15 mmHg or more 4.
- The assignment of the reference-arm should be individualized and not considered as definitive, as the agreement of reference-arm assignment is weak to moderate 3.
Arm Position and Blood Pressure Measurement
- The position of the arm during blood pressure measurement is important, as placing the arm below the right atrial level can result in spuriously elevated BP values 5, 6.
- Both systolic and diastolic blood pressures are significantly higher when the arm is placed on the arm-rest of a chair than at the right atrial level 6.
- The position of the body and the arm during indirect blood pressure measurement can influence BP readings, and should be precisely mentioned in every study reporting BP values 5.