Blood pressure assessment in severe obesity: validation of a forearm approach

Obesity is frequently associated with systemic hypertension. Blood pressure measure is inaccurate in severely obese patients because of poor cuff size fitting. The aim of the study is to assess the degree of agreement between the intra-arterial method as the gold standard vs. noninvasive methods, i.e., forearm blood pressure and upper-arm blood pressure measures.

A total of 1285 measures of intra-arterial and forearm blood pressure were taken in 51 severely obese patients in a supine position in the operating and the recovery room. A subset of 352 upper-arm measures were taken in the recovery room and compared to the intra-arterial and the forearm methods.

Correlation between the intra-arterial and the forearm measures was 0.90 (P < 0.001) for the 2570 data (systolic and diastolic). Compared to intra-arterial, the forearm method overestimated systolic (6 ± 16 mm Hg, P < 0.001) and underestimated diastolic blood pressure (2 ± 11 mm Hg, P = 0.03). Compared to intra-arterial, upper-arm underestimated systolic (8 ± 16 mm Hg, P < 0.01) and overestimated diastolic blood pressure (9 ± 7 mm Hg, P < 0.001).

The magnitude of differences between the intra-arterial and forearm method was less than differences between the intra-arterial and upper-arm method. Our results suggest that forearm method may be a more accurate alternative to upper-arm measurement to assess blood pressure in severely obese patients.