Local Thermal Impact on Microcirculation Assessed by Imaging Photoplethysmography

Abstract

Laser Doppler Flowmetry and Laser Speckle Contrast Imaging are applied usually for assessment of parameters of the cutaneous blood flow during thermoregulation. Alternatively, this work explores the feasibility of blood pulsation imaging under incoherent green illumination for measuring the response of human body on local thermal impact. The proposed technique allows assessment of the cutaneous blood flow changes during thermoregulation simultaneously in different areas of the body. The preliminary experiments show that the blood pulsation amplitude (BPA) is sufficiently reliable index, which could characterize the relative change of the cutaneous blood flow similarly to the parameter measured with the Laser Doppler Flowmetry technique. It is shown that BPA grows up proportionally to the skin temperature increase in the preliminary cooled finger, whilst it is in the steady state in another finger having the constant temperature. The rate of BPA increase is individual characteristic of a subject, which could serve as a parameter of the subject's vasomotor reactivity on the temperature changes. High quality of visualized distribution of blood pulsations, good repeatability of the BPA, and revealed dependencies of its response on the skin-temperature change offer the prospect for development new system of studying microcirculation.

Remote Photoplethysmography for Evaluation of Cutaneous Sensory Nerve Fiber Function

“…The cost-effective alternative could be remote photoplethysmography [ 26 ], which is a contactless optical technique for blood volume pulsation detection in the tissue using various computational algorithms [ 27 ] and relatively simple instrumentation: video camera, to detect subtle variations of back-reflected light, and appropriate light source. Currently, the imaging photoplethysmography (iPPG) is expanding its applications beyond the assessment of heart rate and arterial stiffness, illustrated by previous studies such as studies of Kamshilin et al suggesting the high clinical potential of remote photoplethysmography in the evaluation of cutaneous vasomotor responses [ 27 , 28 , 29 , 30 , 31 , 32 ]. However, further refinement of this approach requires alteration of small sensory nerve fiber function in a controllable manner, which is difficult to achieve in neuropathic patients due to differences in etiology, degree of dysfunction, comorbidities, and other factors [ 33 ].…”

Contactless Monitoring of Microcirculation Reaction on Local Temperature Changes

“…It should be noted that our previous experiments, in which applicability of an IPPG system to assess the microvasculature response on the temperature changes [12] was demonstrated, were carried out in conditions under which the temperature of a preliminarily-cooled finger was increased due to internal heating. In contrast, here we assessed the microcirculation reaction to the external local thermal impact with the temperature exceeding the skin temperature.…”

“…Particularly, it was shown that changes in skin blood flow measured by LDF and PPG are related to changes in the skin temperature [11]. Recently, the possibility of quantifying the change in blood microcirculation with local temperature effects on the human hand has been demonstrated by using the imaging photoplethysmography (IPPG) system [12]. It is worth noting that the PPG waveform was measured by Kamshilin et al [12] only afterwards the thermal impact.…”

“…Recently, the possibility of quantifying the change in blood microcirculation with local temperature effects on the human hand has been demonstrated by using the imaging photoplethysmography (IPPG) system [12]. It is worth noting that the PPG waveform was measured by Kamshilin et al [12] only afterwards the thermal impact. However, monitoring of the processes before, during, and after temperature changes would provide more information about the vascular processes.…”

Novel contactless approach for assessment of venous occlusion plethysmography by video recordings at the green illumination

“…Investigation of the skin and muscular vessels reaction on differential provocations is very useful for deeper understanding of the PPG signal origin. For example, local change of the skin temperature results in local change of blood flow in the dermis 30 affecting the PPG signal 31 , whereas global hypothermia affects the blood flow in muscular vessels, which maximally contribute to the volumetric blood flow of the forearm 32 . In our extended experiment, the skin temperature was the same.…”