Although surgical lasers can be defo- cused and arranged to give energy den- sities in the low level range, superlumi- nous diodes (SLDs, also known as light therapy) can deliver the same power and wavelengths much more economically and more safely. CEllUlar mECHanism Light energy consists of photons or packets of electromagnetic energy. The number of photons and the photons’ wavelength will determine the energy delivered to the tissue being irradiated. This energy is either absorbed by tis- sues and cells or scattered within the body to eventually become absorbed. The light energy is absorbed by chro- mophores or photoacceptors. Tissues have optical properties and their light absorption ability is wavelength depen- dent. In animals and humans the most effective wavelengths are in the red and near infrared (NIR) light range (600 to 950 nanometres). Cells and tissues that are compromised as a result of ischemia, inflammation and edema appear to be more receptive to the photons compared to normal cells. These injured cells ap- pear to have a lower threshold to the stimulation of laser light. It has been suggested that the mecha- nism of low level laser is based on the absorption of photons by chromophores of the respiratory chain. The mitochon- drial membrane has complex proteins (NADH dehydrogenase, succinate dehy- drogenase, cytochrome c reductase, cy- tochrome c oxidase and ATP synthase), which are electron or proton transfer proteins helping to produce energy for many biological functions. Cytochrome c oxydase and nitric oxide synthase are particularly reactive to photon stimula- tion. The resultant increase in ATP mol- ecules and nitric oxide enhances cellular metabolism, circulation and nerve func- tion. Since many of the reactive proteins are enzymes, low level laser therapy helps in the treatment of neuromusculo- skeletal conditions in three ways: (1) an- ti-inflammation, (2) pain reduction, (3) tissue healing. Richard Martin in Prac- tical Pain Management, Nov/Dec 2003, outlines these very effectively. anTi-inflammaTion • Stabilization of cellular membrane Ca++, Na+ and K+ concentrations. 30 • CANADIAN CHIROPRACTOR | FEBRUARY 2010 • Production and synthesis of ATP is enhanced • Vasodilation reduces ischemia and increases perfusion • Acceleration of leukocytic activity • Increased prostaglandin pro- duction • Reduction in Interleukin 1 • Enhanced lymphocyte response • Increased angiogenesis for both blood and lymphatic capillaries • Temperature modulation • Enhanced Superoxide Dismutase levels • Decreased C reactive protein levels Pain rEdUCTion • Increase in b-Endorphins • Suppression of C fiber afferent excitation • Increase Nitric oxide production • Restoration of nerve cell action potential • Axonal sprouting and nerve cell regeneration • Decreased bradykinin levels • Increased release of acetylcholine • Normalization of Ca++, Na+ and K+ ions concentrations TissUE HEaling • Enhanced leukocyte infiltration • Increased macrophage activity • Increased neovascularization • Increased fibroblast proliferation • Keratinocyte proliferation • Early epithelialization • Growth factor increases • Enhanced cell proliferation and differentiation • Greater healed wound tensile strength CHiroPraCTiC and ligHT THEraPy Although researchers in the field of laser therapy have no doubt that lasers have come of age and are a viable adjunct in the management of neuromusculoskeletal conditions, there are still a lot of unan- swered questions. As clinicians, chiro- practors are concerned about the dosage, wavelength, treatment duration, depth of penetration, pulsed versus non-pulsed machines, high powered lasers versus su- perluminous diodes and how to fit these therapies into our existing treatment pro- tocols. This is a rapidly expanding field and, as more research is undertaken, more of these questions will be answered. Researchers have established that for our purposes wavelengths in the 600 to 950 nanometres range are most effective. Determining the right dosage has been likened to watering a lawn. Too little wa- ter and the lawn remains parched, while too much water creates a mud bath. Re- cent research has also ascertained that the physiological changes mentioned above are more likely to occur when the tissue treated can absorb approximately four to six joules of energy per square centimetre. Considering the dosage re- quirements, SLDs can deliver this in three minutes for more proximal tissues and, in the odd case when deeper tissues are being treated, treatment times can be extended. assEssing THE TECHnology This brings up the next question that clinicians need to ask themselves. What machine do I buy? Early laser machines were very expensive and this trend has continued putting them out of reach for many chiropractors. The development of SLDs has now made low level energy laser therapy affordable for everyone. Of course, the question for many is how can machines with such a disparity in price deliver the same benefits. Dr. Tina Karu, a top laser researcher from Finland, writes, “Coherent properties of laser light are not important when cellular mono- layers, thin layers of cell suspension as well as thin layers of tissue surface, are irradiated. In these cases, the coherent and non-coherent light (i.e., both lasers and LED’s) with the same wavelength, intensity and dose provides the same biological response.” Another important feature of SLDs is their safety. Coher- ent light beams can cause retinal dam- age so safety goggles should be worn by the treating practitioner and the patient whereas non-coherent light from SLDs do not cause retinal damage. Low level laser therapy has a bright spot in chiropractic’s future. When you look at this form of treatment, it fits right in with the basic philosophy of chiro- practic. Light beams, like chiropractic, provide a natural non-invasive form of treatment that helps the homeostatic properties of the body heal itself. It is now up to us to learn more about this effective form of treatment and hopefully conduct research and add to the existing body of knowledge. • www.canadianchiropractor.ca
Chiropractic + Naturopathic Doctor February 2010: Page 30
