Digital thermal monitoring (DTM) of vascular reactivity closely correlates with doppler flow velocity

Abstract

The noninvasive measurement of peripheral vascular reactivity, as an indicator of vascular function, provides a valuable tool for cardiovascular screening of at-risk populations. Practical and economical considerations demand that such a test be low-cost and simple to use. To this end, it is advantageous to substitute digital thermal monitoring (DTM) for the more costly and complex Doppler system commonly used for this measurement. A signal processing model was developed to establish the basis for the relationship between finger temperature reactivity and blood flow reactivity following a transient brachial artery occlusion and reperfusion protocol (reactive hyperemia). Flow velocity signals were acquired from the radial artery of human subjects via an 8 MHz Doppler probe while simultaneous DTM signals were acquired from a distal fingertip via DTM sensors. The model transforms the DTM temperature signals into normalized flow signals via a deconvolution method which employs an exponential impulse function. The DTM normalized flow signals were compared to simultaneous, low-frequency, normalized flow signals computed from Doppler sensors. The normalized flow signals, derived from DTM and Doppler sensors, were found to yield similar reactivity responses during reperfusion. The reactivity areas derived from DTM and Doppler sensors, indicative of hyperemic volumes, were found to be within ± 15%. In conclusion, this signal processing model provides a means to measure vascular reactivity using DTM sensors, that is equivalent to that obtained by more complex Doppler systems.

New Indices of Endothelial Function Measured by Digital Thermal Monitoring of Vascular Reactivity: Data from 6084 Patients Registry

“…During the cuff occlusion period, fingertip temperature in the right hand decreased because of the absence of warm circulating blood. When the cuff was released after the 5-minute occlusion, hyperemic blood flow to the forearm and hand was restored, and this resulted in a “temperature rebound” in the fingertip that is directly related to the subject's hyperemic blood flow response, endothelial function, and vascular reactivity [21, 22]. Using the recorded fingertip temperatures, the ambient temperature of the testing room, the observed slope of temperature decline, and a multivariate bioheat formula, the VENDYS software calculated and plotted a zero reactivity curve (ZRC).…”

Assessment and Prognosis of Peripheral Artery Measures of Vascular Function

“…An automated device that controls for systemic sympathetic effects by utilizing data from the non-occlusion finger allows for calculation of the adjusted temperature rebound (aTR). 72 This response has been shown to be abnormal in subjects with various risk factors including diabetes, insulin-resistance and CAD. 73 It has also been shown to be related to the presence of myocardial perfusion defects and obstructive CAD as detected by nuclear scintigraphy and computed tomography coronary angiography respectively.…”

Evaluation of Digital Thermal Monitoring as a Tool to Assess Perioperative Vascular Reactivity

“…While FMD is a non-invasive measurement of vascular reactivity and endothelial-dependent vasomotion 6) , this technique is dependent on technical expertise and expensive ultrasound equipment, thereby restricting it to a vascular research laboratory and therefore being of limited clinical utility in the perioperative setting. DTM, a novel non-invasive technique, utilizing the principle of reactive hyperemia, has also been shown to correlate with Doppler flow velocity 19) , a parameter used in the BART technique. Recent studies investigating DTM showed that impaired vascular reactivity correlated with the extent of myocardial perfusion defect 20) and was found in patients with metabolic syndrome and diabetes mellitus 21) ; however, these lat- compared to their cohorts without obesity.…”