BACKGROUND:Near-infrared spectroscopy (NIRS) is a non-invasive and convenient tool which measures cerebral blood flow changes.In spite of its usefulness to evaluate brain functions, it is known that NIRS signals are affected by not only neural activities but also cardiovascular hemodynamics such as heartbeats.Therefore, it is important to clarify the influence of cardiovascular hemodynamics, such as cardiac output and stroke volume, on NIRS signals.METHODS:We measured NIRS signals and cardiovascular hemodynamic signals simultaneously during isometric exercise and postural change with keeping head angle in order to evaluate the influences of cardiovascular hemodynamic variables on NIRS signals independently.RESULTS and DISCUSSION:Cardiac output and the average of NIRS signals were both increased by the isometric exercise. In addition, stroke volume and the amplitude of NIRS signals, which is caused by heartbeats, were both increased by the tilt down. Therefore the average of NIRS signals would be affected by cardiac output and position of lower limbs independently.ACKNOWLEDGEMENTS:This research was partly supported by JST PRESTO and SCOPE.
