Comparison of forearm and upper arm blood pressures

OBJECTIVE: In the prehospital setting it is not always feasible to obtain blood pressure (BP) readings from the upper arm. This study was performed to compare BPs obtained from subjects' forearms and upper arms in order to assess the utility of forearm BP as a surrogate for standard BP. METHODS: The authors performed a prospective, cross-sectional, convenience study in a sample of ambulatory university ED patients, where each subject had sequential determinations of left upper arm and forearm BPs with an automated monitor at ED triage. The order of measurement was determined by the day of the week. Demographic and clinical data were also recorded. The main outcome measure was the correlation between upper arm and forearm systolic and diastolic BPs. Pearson's correlation coefficient and Student's t-test were used to analyze the data. RESULTS: 151 patients were enrolled. The mean age was 35.3+/-15.7 years; 40% were female and 78% were white. The mean forearm and upper arm systolic BPs were 129.8+/-20.7 mm Hg and 126.2+/-17.6 mm Hg (p = 0.002). The mean forearm and upper arm diastolic BPs were 80.7+/-14.5 mm Hg and 76.8+/-13.4 mm Hg (p<0.001). The correlations between forearm and upper arm systolic and diastolic BPs were 0.75 (p<0.001) and 0.72 (p<0.001). The differences between forearm and upper arm systolic and diastolic BPs were within 20 mm Hg in 86% and 94% of patients, respectively. CONCLUSION: Forearm BP is a fairly good predictor of standard upper arm BP in most patients. Forearm BP may be used when measurement of upper arm BP is not feasible.