Figure 6.

Subject averaged response to the pressure modulation maneuver. (A) Measured hemodynamic response to 30 s of tourniquet tightening. Using the ratio of the relative decrease between the long channel (39.2%) and the short channel (85.3%), the sensitivity of the long channel to the scalp blood flow can be estimated to be 46%. For long separation DCS measurements, brain sensitivity has been shown to be inversely proportional to scalp sensitivity⁶⁶, and we can estimate that the 35 mm separation measurement has a brain sensitivity > 50%. (B) For this maneuver, as expected, the systemic physiology was not significantly affected by the tightening of the tourniquet on the forehead.