Page 13 - Veterinary Laser Therapy in Small Animal Practice

Introduction: light as a healing tool

One brute fact on which the rest of this book builds is anti-inflammatory effect is based both in the metabolic
that light can cause physiological changes in the body. improvement of the tissue (more oxygen, more ATP)
The extent of these changes will be explored much fur- and the decrease in inflammatory mediators.
ther, but if you have trouble with this basic premise, Of course different tissues exhibit their particulari-
try reconciling our ability to see without first accepting ties in the healing or repair process: wound healing is
that light can initiate chemical reactions that lead to different from bone healing. Tissue proliferation may
electrical impulses (and as it turns out, vice versa) that take days to weeks, and may be achieved by primary or
deeply affect our living selves. secondary healing. Both involve fibroblast recruitment,
A long time ago, however, people realized that the extracellular matrix deposition, and angiogenesis; LT
human eye only sees a fraction of the light around us. influences all of these processes, from new blood vessel
Among other things, this usually obstructs our under- formation, fibroblast proliferation, differentiation, and
standing that different kinds of light can penetrate migration, to osteoblastic activity as well as collagen
through things that visible light cannot. Eventually the production. [2]
field of radiography was born, and now we take this Laser increases platelet-derived growth factor
idea as a given. But you picked up this book to learn (PDGF) and basic fibroblast growth factor (bFGF),
about a different flavor of light (the infrared) and what among other growth factors, which have a stimulating
[3]
kind of physiological changes it can initiate that can effect on the growth of fibroblasts. The magnitude of
help your patients. The hallmarks of laser therapy (LT) this increase is about threefold to sixfold compared to
[4]
are how it helps in different stages of healing, as well as control cultures in some studies. There will be more
its anti-inflammatory and analgesic properties. These fibroblasts, and they will be working more efficiently,
are interrelated, since tissue healing involves a certain producing more collagen. [5, 6] Not all collagen is the
degree of inflammatory response, and more inflamma- same, though. In the earlier stages of tissue healing the
tion usually means more pain (not this simple, but we synthesis of type III collagen is higher, but then a lot
will discuss this in detail later). of this is gradually replaced by type I collagen fibers,
Tissue healing involves hemostasis, inflammation, a which are more resistant, better organized, and also
variable amount of debridement/resorption, prolifera- predominate in normal intact tissue. LT improves
tion, and remodeling or maturation. Briefly, what we tensile strength by increasing the amount of type I col-
see in practice is that LT makes tissue leave the inflam- lagen. [7, 8] This remodeling phase starts while prolifera-
matory phase to go into the repair (anabolic) phase tion is still happening, but can go on for months. More
faster, progressing to its own homeostasis. In an acute extracellular matrix is synthesized, but at the same
injury this means faster healing; chronic inflammation time degraded, and cellularity and vascularity decrease.
leads to non-healing ulcers, degenerative diseases, and There is further contraction in the case of wounds, and
chronic pain, to mention a few, so exiting that state if the process happens correctly, the resulting tensile
is also a basic and general therapeutic target. This strength increases because of a proper alignment of

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