The thermal impact of phototherapy with concurrent super-pulsed lasers and red and infrared LEDs on human skin

Abstract

From the very first reports describing the method of action of phototherapy, the effects have been considered to be the result of photochemical and photophysical interactions between the absorbed photons and tissue and not related to secondary changes in tissue or skin temperature. However, thermal effects have been recently reported in dark pigmented skin when irradiated with single wavelengths of 810 and 904 nm of low-level laser therapy (LLLT) devices even with doses that do not exceed those recommended by the World Association of Laser Therapy (WALT). The aim of this study was to evaluate the thermal impact during the concurrent use of pulsed red and infrared LEDs and super-pulsed lasers when applied to light, medium, and dark pigmented human skin with doses typically seen in clinical practice. The study evaluated the skin temperature of 42 healthy volunteers (males and females 18 years or older, who presented different pigmentations, stratified according to Von Luschan's chromatic scale) via the use of a thermographic camera. Active irradiation was performed with using the multi-diode phototherapy cluster containing four 905-nm super-pulsed laser diodes (frequency set to 250 Hz), four 875-nm infrared-emitting diodes, and four 640-nm LEDs (manufactured by Multi Radiance Medical™, Solon, OH, USA). Each of the four doses were tested on each subject: placebo, 0 J (60 s); 10 J (76 s); 30 J (228 s); and 50 J (380 s). Data were collected during the last 5 s of each dose of irradiation and continued for 1 min after the end of each irradiation. No significant skin temperature increases were observed among the different skin color groups (p > 0.05), age groups (p > 0.05), or gender groups (p > 0.05). Our results indicate that the concurrent use of super-pulsed lasers and pulsed red and infrared LEDs can be utilized in patients with all types of skin pigmentation without concern over safety or excessive tissue heating. Additionally, the doses and device utilized in present study have demonstrated positive outcomes in prior clinical trials. Therefore, it can be concluded that the effects seen by the concurrent use of multiple wavelengths and light sources were the result of desirable photobiomodulation effect and not related to thermal influence.

Does the combination of photobiomodulation therapy (PBMT) and static magnetic fields (sMF) potentiate the effects of aerobic endurance training and decrease the loss of performance during detraining? A randomised, triple-blinded, placebo-controlled trial

“…Therefore, predicting a 20% sample loss, up to 72 healthy and physically inactive male volunteers aged 18-35 years who were students at the Nove de Julho University, would be recruited for the study to ensure a final sample size of 60 volunteers. As the PBMT/sMF device used in the study has no harmful thermal effects, volunteers of all ethnicities were recruited [28].…”

Photobiomodulation Therapy Improves Performance and Accelerates Recovery of High-Level Rugby Players in Field Test: A Randomized, Crossover, Double-Blind, Placebo-Controlled Clinical Study

“…PBMT may prevent the onset of fatigue during activity thereby improving athletic performance (20). PBMT is non-thermal (11), commercially available modality that can be used in a variety of clinical and athletic settings. The effects of PBM are related to photochemical and photobiological effects within the tissue and are not attributed to heat (11).…”

“…PBMT is non-thermal (11), commercially available modality that can be used in a variety of clinical and athletic settings. The effects of PBM are related to photochemical and photobiological effects within the tissue and are not attributed to heat (11). PBMT modulates biological processes of cells on mitochondrial level, increasing the oxygen consumption and production of adenosine triphosphate (ATP) (13).…”

Effects of photobiomodulation therapy combined to static magnetic field in strength training and detraining in humans: protocol for a randomised placebo-controlled trial

“…As previously demonstrated by Joensen et al 32 some PBMT devices can significantly increase skin temperature, promote discomfort and even lead to interruption of treatment/irradiation in patients with darker skin. However, since the PBMT/sMF device used in the study does not cause any significant increase in skin temperature nor harmful thermal effects in light, medium or dark human skin,33 volunteers of different skin colours will be recruited. Volunteers will be informed about all study procedures and asked to sign the informed consent form prior to their enrolment in the study.…”