Blood pressure measurement in obese patients: comparison between upper arm and forearm measurements

BACKGROUND: It is well known that blood pressure measurement with a standard 12-13 cm wide cuff is erroneous for large arms. OBJECTIVE: To compare arm blood pressure measurements with an appropriate cuff and forearm blood pressure measurements (BPM) with a standard cuff, and both measurements by the Photopletismography (Finapres) method. METHODS: One hundred and twenty-nine obese patients were studied (body mass index=40+/-7 kg/m2). The patients had three arm BPM taken by an automatic oscillometric device using an appropriate cuff and three forearm BPM with a standard cuff in the sitting position after a five-minute rest. Data were analysed by the analysis of variance. The correction values were obtained by the linear regression test. RESULTS: Systolic and diastolic arm BPM with an appropriate cuff were significantly lower (p<0.05) than forearm BPM with a standard cuff. The measurements obtained by Finapres were significantly lower (p<0.05) than those found for forearm systolic and diastolic blood pressures and upper arm diastolic blood pressure. The equation to correct BPM in forearm in obese patients with arm circumference between 32-44 cm was: systolic BPM=33.2+/-0.68 x systolic forearm BPM, and diastolic BPM=25.2+0.59 x forearm diastolic BPM. CONCLUSION: This study showed that forearm blood pressure measurement overestimates the values of arm blood pressure measurement. In addition, it is possible to correct forearm BPM with an equation.