Method for the measurement of the sensitivity of vascular beds to ischemia

We identify a novel performance parameter of arterial beds and propose a convenient, non-invasive method for its measurement. The parameter relates the amount of reactive hyperemic flow that ensues after blood flow occlusion to the duration of occlusion and thus may be viewed as a measure of the sensitivity of the downstream vascular bed to the level of ischemia. The measurement is performed by inducing three successive progressively longer periods of ischemia in a limb using a pneumatic cuff. During the periods between occlusions, reactive hyperemic flow is measured at a finger using laser Doppler fluximetry (LDF). Total hyperemic response is calculated for each occlusion by averaging the LDF time series over the interocclusion interval. The vascular sensitivity parameter is calculated as the gradient of the line fit to the three mean response measurements. We evaluate the method in 18 subjects and find that orally administered nicotine significantly reduces the sensitivity to ischemia by 34%.