Flow ratios to express results obtained with the human in vivo 'perfused forearm technique'

Aims To determine the accuracy of forearm blood flow (FBF) ratio (flow in i nfused arm/flow in control arm) to detect unilateral increases in forearm b lood flow. Methods In nine healthy male volunteers, we measured the effect of infusion of saline into the brachial artery at a rate of 2 ml/100 mi forearm min(-1 ) on FBF ratio during control, mental arithmetic (MAR) and lower body negat ive pressure (LBNP) at -40 mmHg. Results Saline infusion increased FBF ratio from baseline by 115.9 +/- 17.4 , 82.0 +/- 19.0 and 159.6 +/- 53.3% for control, MAR and LBNP, respectively (p < 0.05 for MAR vr control). Conclusions FBF ratio may underestimate unilateral increases in forearm blo od flow during simultaneous mental arousal.