Clinical comparison of automatic, noninvasive measurements of blood pressure in the forearm and upper arm with the patient supine or with the head of the bed raised 45°: A follow-up study

BACKGROUND: Noninvasive measurement of blood pressure in the forearm is used when the upper arm is inaccessible and/or when available blood pressure cuffs do not fit a patient's arm. Evidence supporting this practice is limited. OBJECTIVE: To compare noninvasive measurements of blood pressure in the forearm and upper arm of medical-surgical inpatients positioned supine and with the head of the bed raised 45°. METHODS: Cuff size was selected on the basis of forearm and upper arm circumference and manufacturers' recommendations. With a Welch Allyn Vital Signs 420 Series monitor, blood pressures were measured in the forearm and then in the upper arm of 221 supine patients with their arms resting at their sides. Patients were repositioned with the head of the bed elevated 45° and after 2 minutes, blood pressures were measured in the upper arm and then the forearm. Starting position was alternated on subsequent subjects. RESULTS: Paired t tests revealed significant differences between systolic and diastolic blood pressures measured in the upper arm and forearm with patients supine and with the head of the bed elevated 45°. The Bland-Altman procedure revealed that the distances between the mean values and the limits of agreement were from 15 to 33 mm Hg for individual subjects. CONCLUSIONS: Noninvasive measurements of blood pressure in the forearm and upper arm cannot be interchanged in medical-surgical patients who are supine or in patients with the head of the bed elevated 45°.