Individual Skin Temperature is Associated with the Microcirculatory Response to Photobiomodulation: A Randomized Controlled Study

Background: Photobiomodulation (PBM) has been shown to increase blood flow. Using laser Doppler flowmetry we have previously demonstrated that 5 minutes of PBM irradiation with non-coherent light sources, has immediate vasodilative effects that enhances downstream tissue perfusion. In the present study we characterized the microcirculatory response to PBM by thermal imaging.

Methods: Twenty healthy non-smoking volunteers without any known vascular pathologies were randomized to receive a 5 minute continuous irradiation over the wrist area (wavelength=630nm or 830nm, power density=70mW/cm² or 55mW/cm² respectively, OmniLux New-U [Photomedex, USA]). Thermal images of both hands were taken every minute, before- and during irradiation, and for 20 minutes follow-up.

Results: PBM in both wavelength resulted in a significant mean skin temperature increase that began during irradiation, and remained high 20 minutes without irradiation when the session ended (p0.5˚C) was observed in only 10 of the 20 subjects. The response (temperature change) was larger in distal compared to proximal areas (fingers vs hand center, mean±SD: 3.8±2.6˚C vs 1.8±1.2˚C). Non-responders could be sub-categorized as having ‘hot’ hands (>37.5˚C baseline temperature) or ‘cold’ hands (<33˚C), with the latter even presenting a decrease in skin temperature in response to PBM.

Conclusions: Using thermal imaging, we found that the microcirculatory response to PBM is dependent on the baseline skin temperature. This individual response to PBM may pave the way to personalized protocols.