Possibility of Evaluation for Peripheral Vasodilation during Reactive Hyperemia by Near-Infrared Spectroscopy

Abstract

The purpose of this study was to examine the usefulness of near-infrared spectroscopy (NIRS) for evaluating peripheral vasodilation during reactive hyperemia. Thirty female patients (younger women with mean age of 22 yrs, n=10; middle age women with a men age of 41 yrs, n=10; older women with a mean age of 62 yrs, n=10.) participated in this study. All older women were postmenopausal. Blood pressure (BP) and cardio ankle vascular index (CAVI) were measured at rest and NIRS signals were measured in the forearm during reactive hyperemia after 5 min arterial occlusion. CAVI and recovery time of oxygenated hemoglobin (HbO₂) in older women were impaired compared to younger women. Moreover, initial increase in total Hb after cuff deflation indicated total blood volume changes in younger women were significantly greater than older women. There was a significant relationship between HbO₂ recovery time and systolic BP. These results indicate that older women exhibit a delayed HbO₂ response during reactive hyperemia. We suggest that these alterations in HbO₂ kinetics are indicative of microvasculature dysfunction in these subjects and NIRS might be a potential tool to evaluate peripheral vasodilation.