The use of laser biostimulation in human and animal physiotherapy – a review

Laser biostimulation involves applying a laser beam to the tissue to facilitate healing and regenerative processes. Laser therapy is one of the most important physical methods used in human physiotherapy. In veterinary medicine, laser therapy is a new and so far poorly examined method. The results of studies conducted so far are very promising, yet the positive effect of laser light, especially that of class IV, has yet to be confirmed. This article presents an overview of the available literature on the effect of laser treatment on the human and animal organism. Low level laser therapy (LLLT), high intensity laser therapy (HILT), physical therapy The history of laser radiation goes back to 1917 when Albert Einstein discovered the phenomenon of stimulated emission (Riegiel and Sephion 2007). Since then, there have been efforts to create a device emitting laser radiation. In 1960 at Hughes Research Laboratories in Malibu, Theodor Mainman made the first active laser with a wavelength of 693.3 nm (Glinkowski and Pokora 1995), which paved the way for rapid development in this area. The term LASER is an acronym of “light amplification by stimulated emission of radiation”. The most important features of laser include monochromatism, collimation, and coherence of a beam. As a result, it can deliver large amounts of energy to a welldefined place in a short time (Kitchen and Partridge 1991). Currently, laser light is used in almost all areas of medicine. The effects of tissue photodestruction and photocoagulation are used in surgery as they enable precise incision with limited bleeding during surgery. In oncology, laser light is used for photodynamic therapy and photodynamic diagnosis of tumours. In physiotherapy, laser photobiostimulation is carried out to accelerate the regenerative processes in damaged tissue (Fiodor et al. 1995; Mikołajewska 2011). Photobiostimulation has anti-inflammatory, analgesic, antioedema and regenerative effects. It causes an increase in cell metabolism, changes in the structure and function of biological membranes, increased enzyme activity and the release of endorphins, vasodilation and angiogenesis, and increased reproductiveness and activity of immune cells (Riegiel and Sep hion 2007). Until recently, treatment with class IIIB lasers with a power not exceeding 500 mW, also called low-level laser therapy (LLLT), was used. This type of laser therapy does not increase the temperature of irradiated tissue above 1 °C (Ward et al. 2009). The development of new technologies in recent years has allowed for the invention of therapeutic laser devices with a much higher power (class IV lasers), which are currently applied not only in surgery but also in laser therapy (high intensity laser therapy, HILT). During HILT, temperature in the treatment area rises, which increases the intensity of the metabolic process in cells ACTA VET. BRNO 2017, 86: 91–96; https://doi.org/10.2754/avb201786010091 Address for correspondence: Paulina Zielińska Katedra i Klinika Chirurgii Wydział Medycyny Weterynaryjnej Uniwersytet Przyrodniczy we Wrocławiu Plac Grunwaldzki 51, 50-366 Wrocław Telephone: +48 536 26 77 22 E-mail: paulina.zielinska@up.wroc. pl http://actavet.vfu. cz/ (Łukowicz et al. 2007). With the appropriate wavelength and high peak pulse power (3 kW), HILT allows for deeper tissue penetration and stimulation of body structures such as large and deep joints and extensive muscle parts (Zati and Valent 2006). This article provides an overview of available publications concerning the scope and impact of low and high intensity laser therapies on the human and animal body. In vitro study and labolatory animal testing The positive effect of laser therapy on the organism observed in clinical trials gave rise to more detailed study of cells and tissue exposed to laser radiation. In vitro studies on fibroblasts and endothelial cells isolated from the skin and aorta of C3H mice irradiated with red and infrared laser light have shown that the higher the wavelength of the red light, the more effective is the growth of fibroblasts. The optimal length for the endothelial cells was 655 nm, and the wavelength of 810 nm inhibited growth of both endothelial cells and fibroblasts (Moore et al. 2005). Another study evaluated in vitro the effect of laser radiation on the acethylcholinesterase (AChE) activity in erythrocyte membranes. The red cells were exposed to laser radiation at a wavelength of 808 nm and 905 nm with variable parameters. Authors indicated that the laser biostimulation caused changes in AChE activity depending on the parameters used. The highest increase of AChE activity was obtained using laser light with the wavelength of 905 nm and 1,000 Hz or 2,000 Hz with the peak pulse power of 1,100 mW and energy dose of 3J (Pasternak 2012). Renno et al. (2011) demonstrated a positive effect of laser radiation with a wavelength of 660 nm on the granulation and epidermisation of second-degree burn wounds in rats. Similar results were obtained by Voronkov et al. (2014), who exposed the surface of burn wounds in rabbits to red and near-infrared laser radiation and observed a significantly reduced infiltration of tissue with leukocytes, reduced swelling of the dermis and much more numerous and more organized collagen fibres than in the control group. Also Kovács (2015) in her studies observed a positive influence on deep, extended wound healing after LLLT treatment with a wavelength of 810 nm in 5 dogs. Laser radiation with wavelengths of 600 nm and 684 nm at 7.5 J/cm2 of carrageenan-induced rat paw oedema effectively reduced the formation and size of the oedema and migration of inflammatory cells (Albertini et al. 2007). Laser photobiostimulation with a wavelength of 830 nm at 4 J/cm2 of damaged tibialis anterior muscles in rabbits effectively reduced inflammation in the injured tissue, and significantly increased the level of myogenin in the treatment group compared to the control group (Pertille et al. 2012). Similar results were obtained by Rodrigues et al. (2013), who exposed damaged tibialis anterior muscles in rats with a wavelength of 660 nm at 10 J/cm2 and 50 J/cm2. Both Albertini et al. (2007) and Rodrigues et al. (2014) demonstrated that LLLT reduces immunoexpression of COX-2 in damaged muscles, thus decreasing the severity of inflammation and facilitating tissue repair processes. Tests were performed on the safety of high-intensity laser therapy in which 8 cm2 of the back of mice were irradiated twice a week for six months. Two wavelengths, 585 nm and 1320 nm, were used at various energy doses ranging from 8 to 20 J/cm2. Both during and after the test, there were no deaths, symptoms of intoxication, or neoplastic processes in any of the mice (Chan et al. 2007).