The normal range for inter-arm differences in blood pressure.

OBJECTIVE: to establish the mean and normal range for the difference in simultaneous systolic and diastolic blood pressure measurements between the right and left arm. SUBJECTS: 462 subjects, age range 20-89 years, in sinus rhythm and with no history of stroke, 98 of whom had a history of cardiovascular disease or were taking vasoactive medication. METHODS: four simultaneous recordings of blood pressure in both arms were made using two automated sphygmomanometers with the subject supine after resting for 10 min. RESULTS: inter-arm systolic and diastolic blood pressure differences show a near normal distribution of values. Some individuals had clinically important differences in systolic and diastolic blood pressure between their arms. The magnitude of these differences was not related to the mean baseline blood pressure. Linear regression analysis did not demonstrate any significant relationship between inter-arm systolic or diastolic blood pressure difference and age in patients of either sex. For systolic blood pressure the mean difference between the right and left arm was 1.1 mmHg and the normal range was -9 mmHg to 11 mmHg. For diastolic blood pressure the mean difference was 0 mmHg and the normal range -10 mmHg to 10 mmHg. CONCLUSION: the frequency of significant inter-arm systolic and diastolic blood pressure differences suggests that the blood pressure should be taken in both arms at the initial consultation. At subsequent visits, the arm in which measurements are taken should be recorded in the case notes. The higher of the two readings should be used to guide further management decisions.