Two questions frequently asked by chiropractors to distributors of therapeutic lasers are “Is that a cold laser?” and “How do cold lasers work?” But what are cold lasers, and where do they fit among the variety of lasers available for therapeutic use?
A little history
Originally, the term cold laser was used in the 1970s to distinguish therapeutic lasers from surgical lasers, which were hot or had a thermal effect as a result of the focused average power required to cut and perform surgery. The early therapeutic lasers were of considerably low average power and were often less than 50 milliwatts (mW).
The U.S. Food and Drug Administration (FDA) did not clear any lasers above 500 mW of power until 2004. Therefore, a maximum 500 mW or class 3b became the de facto power level that was equated with non- surgical or “cold” lasers.
Laser myths vs. realities
Because lasers come in a range of forms with various purposes and functions, there is considerable confusion regarding their use and performance. The following are some commonly held misconceptions regarding various types of therapeutic lasers.
Cold lasers cannot burn the skin.
Not true if the laser is a continuous wave laser at the mid-to-upper end of the Class 3b classification. If the laser has a suitable power density and is held in place for a period of time, tissue burns can occur.
Class 3b lasers do not have a thermal effect.
Heat is a by-product of the tissue absorbing the laser emission. The fact that the laser is called a “cold laser” does not mean that it is cold to the patient. In fact, a continuous wave Class 3b laser could burn or cut a patient’s skin.
All Class 4 lasers are surgical lasers and can easily burn or cut a patient.
All surgical lasers are Class 4, but not all Class 4 lasers are surgical lasers. Although some advertising uses the term “Class 4” as a proxy or shorthand for lasers that can burn, it is an inaccurate description if the power density is not taken into account.
Peak power output determines whether a laser is called a cold laser.
The FDA classification is based on the average power produced by the laser. A 45- watt peak power super pulsed laser may produce only 400 mW of average power and therefore is correctly classified as a Class 3b laser, not a Class 4 laser.
Continuous wave Class 4 lasers can easily burn patients.
Continuous wave lasers that produce a thermal effect are safely used by moving the treatment handpiece slowly across the treatment area, rather than kept in one place. Risk is minimized by following proper treatment and safety protocols.
Superulsed Class 4 lasers can easily burn patients.
Super pulsed lasers fire pulses in nanoseconds compared to the thousandths of a second that continuous wave lasers fire. The rapid pulsing dissipates thermal effects so that you can place a super pulsed treatment head on a patient and leave it in place as if it were an actual cold laser.
Calling a Class 4 laser a cold laser makes it one.
A laser either has a thermal effect or it does not. The presence of a thermal effect is not a result of a Class 4 status, but a function of a laser’s energy density.
A laser must be held in one place to achieve maximum results.
While many low-powered lasers must be held in one place to deliver a sufficient quantity of joules (energy) to start the biological cascade of the healing response, a laser with higher average power can produce an effective dosage more rapidly. The practitioner or staff member can move the laser handpiece to completely cover the treatment area while providing the necessary energy density.
Clearing the air
New terminology may be helpful to explain the average power that a laser can produce. A number of manufacturers and researchers are using the term “low level laser therapy” (LLLT) to describe lasers that operate below 500 mW (or Class 3b). The World Association for Laser Therapy (WALT) and the North American Association for Laser Therapy (NAALT) have determined that the proper terminology to use for LLLT is photobiomodulation (PBM).
Laser manufacturers have also begun using terms such as “high power,” “deep penetrating,” and “deep tissue” to describe their Class 4 offerings. And some take the same shorthand approach as those using “cold laser” and simply say “Class 4” to indicate higher power.
The more clinically useful approach is to refer to average power rather than focus on the thermal effects of lasers. Clearer terminology can promote better understanding.
Nelson Marquina, DC, PhD, is the president of USA Laser Biotech Inc. and a developer of biophotonic and bioelectromagnetic systems and treatment protocols. He is also certified by the Virginia Board of Medicine to practice acupuncture.
Rob Berman is a partner at Berman Partners, LLC, a medical device sale, service, and marketing company. Berman Partners specializes in new and preowned therapeutic lasers. He can be contacted at 860-707-4220, [email protected], or through bermanpartners.com.