The effects of anatomical structures on adult forearm and upper arm noninvasive blood pressures

OBJECTIVE: The purpose of this study was to determine the effects of anatomical structures, specifically limb subcutaneous tissue and vessels on differences between forearm and upper arm oscillometric noninvasive blood pressure measurements. METHODS: Nineteen volunteers with a mean age of 21.7+/-3.7 years and without peripheral vascular disease or coronary artery disease participated. Circumference and skinfolds were measured for the upper arm and forearm. Body mass indices were calculated. Ultrasound measured vessel depth and diameter in the upper arm and forearm. Dual energy X-ray absorptiometry determined percentage of subcutaneous tissue in the arm. With participants seated, American Heart Association guidelines were used to measure blood pressures, first by auscultatory method (upper arm only) and then by oscillometric method (upper arm and forearm) with a Dinamap 100 oscillometric blood pressure monitor. RESULTS: Statistically significant differences were seen between upper arm auscultatory and oscillometric systolic blood pressures (t=-4.88; P=0.000) and mean arterial pressures (t=-3.07; P=0.007). Differences between oscillometric forearm and upper arm blood pressure readings were statistically significant for mean arterial pressures (t=-2.39; P=0.028). A regression model suggested that forearm and upper arm vessel depth, forearm vessel diameter, and upper arm circumference explained a statistically significant portion of the difference between forearm and upper arm blood pressures. CONCLUSIONS: Differences between forearm and upper arm oscillometric blood pressures can be partially explained by vessel size, depth and upper arm circumference.