Characterization and reproducibility of forearm arterial flow during reactive hyperemia.

Peripheral arterial flow has been assessed for a variety of indications including characterization of endothelial function during reactive hyperemia. However, quantification of this blood flow as a surrogate remains an imperfect reflection of endothelial function. We sought to better characterize hyperemic reaction to (1) elucidate the influence of the endothelial function and (2) assess the reproducibility of our modeling over time. Sixteen normal subjects underwent simultaneous forearm reactive hyperemia testing with a near-infrared system at baseline, baseline +24 h and baseline +27 h. Baseline flow was measured to 3.6 +/- 0.2 ml dl(-1) min(-1), and was highly reproducible 24 and 27 h later. With reactive hyperemia, the blood flow increased to 20.5 +/- 4.6 ml dl(-1) min(-1). Arterial blood flow curves during reactive hyperemia displayed a bimodal pattern, with the second peak occurring 59.1 +/- 10.6 s after the onset of hyperemia. We believe that this latest peak represents the contribution of endothelial factors to the hyperemic reaction. Modeling of hyperemic curves led to the introduction of a reproducible new parameter (etafactor) that reflects the normalized contribution of this second peak. In conclusion, forearm arterial flow during reactive hyperemia revealed a bimodal distribution where functional interpretation allowed distinction of the two components. Basal flow measurements and results of this modeling were reproducible 24 and 27 h later.