New measures of Digital Thermal Monitoring (DTM), a low cost non-invasive tool to assess vascular health, are developed. Original measures of thermal vascular reactivity tend to be dependent upon the initial vascular state (such as temperature before occlusion).
The objective of this study is to identify new measures that will provide a single independent predictor of vascular health. Full three dimensional simulations were carried out to simulate transient finger tip temperature response during brachial occlusion and reperfusion. These numerical results were validated with patient data and then used to simulate a variety of test cases and discern relationships between the thermal measure and the surge in flow rate (reactive hyperemia).
Defining the zero-reactivity response as the response to a step change in flow rate from near zero back to the original steady state value before occlusion, a reference signal is constructed which accounts for the finger size, thermo-physical properties, external environment and the start temperature (initial vascular state). This reference is used to normalize the temperature reactivity, forming a new measure called adjusted temperature reactivity that is a function of reactive hyperemia only. It is independent of the initial vascular state and external environment, leading to a more robust and reliable measure of vascular health.