Contactless Monitoring of Microcirculation Reaction on Local Temperature Changes

Abstract

Assessment of skin blood flow is an important clinical task which is required to study mechanisms of microcirculation regulation including thermoregulation. Contactless assessment of vasomotor reactivity in response to thermal exposure is currently not available. The aim of this study is to show the applicability of the imaging photoplethysmography (IPPG) method to measure quantitatively the vasomotor response to local thermal exposure. Seventeen healthy subjects aged 23 ± 7 years participated in the study. A warm transparent compress applied to subject’s forehead served as a thermal impact. A custom-made IPPG system operating at green polarized light was used to monitor the subject’s face continuously and simultaneously with skin temperature and electrocardiogram (ECG) recordings. We found that the thermal impact leads to an increase in the amplitude of blood pulsations (BPA) simultaneously with the skin temperature increase. However, a multiple increase in BPA remained after the compress was removed, whereas the skin temperature returned to the baseline. Moreover, the BPA increase and duration of the vasomotor response was associated with the degree of external heating. Therefore, the IPPG method allows us to quantify the parameters of capillary blood flow during local thermal exposure to the skin. This proposed technique of assessing the thermal reactivity of microcirculation can be applied for both clinical use and for biomedical research.

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 ].…”

Association of remote imaging photoplethysmography and cutaneous perfusion in volunteers

“…Recent studies on volunteers and patients affirm the association of iPPG to cutaneous perfusion. The local iPPG signal amplitude is significantly increased by the cutaneous vasomotor response to a circumscribed thermal impact 37 . Moreover, a cold face test in volunteers provoked marked changes in the iPPG signal even in entirely different body regions, indicating that systemic vasoactive events can be detected by iPPG 38 .…”

An iPPG-Based Device for Pervasive Monitoring of Multi-Dimensional Cardiovascular Hemodynamics

“…Kamshilin et al [ 18 ] used the green Light Emitting Diode (LED) equipped with a Complementary Metal Oxide Semiconductor (CMOS) camera to calculate PTT and Blood Pulse Amplitude (BPA) distributions from subjects in sedentary and recumbent positions. However, most current iPPG applications were set up in laboratory environment [ 19 , 20 ].…”