Cold Laser Therapy for Acute and Chronic Pain Management

Introduction

Cold (nonsurgical) Laser therapy is a kind of photobiomodulation (PBM) therapy that can be utilized for the treatment of acute as well as chronic pain. In comparison to alternative therapies such as acupuncture (ca. 8000-3500 B.C.) and chiropractic (1895), as well as Physical Medicine and Rehabilitation (1947) and cold laser therapy was a new development in the field of medical practice. The first cold laser was FDA-approved for pain relief in 2001. Low-level laser therapy (LLLT) is only widely utilized for clinical use in the United States since 2002. Laser therapy with high intensity (HILT) is an emerging technology that came to light with the first published studies in 2009. 1 L.T. that utilizes Lasers of Class II or III (producing approximately 500 watts which is <0.5 Watts of energy) is a non-invasive easy, painless treatment that can be used to treat a range of clinical conditions that are superficial (Tables 1 – 3). 2 It has been marketed as a method that can create analgesia and speed healing when utilized as an adjuvant for both physical and pharmacologic painkillers.

Research has shown that LLLT can help reduce discomfort caused by superficial surgical and medical ailments (e.g., women who suffer from painful nipple syndrome due to prolonged nursing, five plantar fasciitis, six and aiding the healing process of wound seven (see Table 3). LLLT devices use near-infrared or red beam lasers with wavelengths ranging from 600 to 1000 nanometers (nm) ranging from 5 to 500 mW of power.

However, the HILT devices are more efficient class IV lasers that can produce more than 40 W of power at greater wavelengths (e.g., Phoenix Theralase (1275 nm) and CureWave (1280 nm)) and thereby permitting deeper tissues to penetrate (Table 1.). The devices are being introduced as non-invasive treatment options for chronic and acute discomfort requiring deeper tissue penetration (Table 1.). 8 HILT therapy treats joint degeneration and a range of musculoskeletal diseases. 8-11 HILT lasers operate by delivering an irradiated laser beam that has high power that ranges from 20-75 W (which corresponds to the maximum optical power of a pulse) at higher wavelengths (>800 millimeters). 12-13 The most recent HILT device is produced through CureWave Lasers LLC (Dallas) and offers a maximum of 444 W in power with a 1280 nm wavelength. The primary benefit of the CureWave device is that it can be placed close to the skin without burning or overheating it. The wavelength is crucial since higher wavelengths reduce absorbance of the beams by melanin hemoglobin and oxyhemoglobin (Figure 1) and allows for deeper penetration into muscles and soft tissue. With more powerful lasers, which also function at longer wavelengths, HILT devices can effectively stimulate larger tissue areas while penetrating more deeply into the soft tissue (Figure 1).14 Although there are several different commercially-available HILT devices (Figures 2-7), not all of these devices have been approved for clinical use by the FDA.

Proposed Mechanisms of PBM Therapy

PBM treatment has been researched for more than 40 years. The latest version of PBM, Cold laser therapy, has proven to induce an anti-inflammatory impact that promotes the healing of tissues and decreases discomfort. Research in animals suggests that cold lasers can also stimulate the proliferation of fibroblasts and the production of Procollagen Types I and III mRNA. This accelerates the healing of the bone and assists in wound recovery. 15

The proposed mechanism for the action of laser therapy is related to the capacity of injured cells to visible light photons and convert the energy into ATP (Table 4.). Laser stimulation increases your production of ATP by forming reactive oxygen and singlet oxygen species. 15 The cell’s components that absorb light are known as Chromophores (i.e., photo-acceptors, also known as photon receptors) and are found in mitochondria and the cellular membrane. The cell components (e.g., Cytochrome c and flavins, porphyrins, and cytochrome c) also possess light-absorbing capabilities.

The mechanism proposed for LLLT is linked to the electronic excitation of chromophores by the cytochrome c oxidase (unit IV of the mitochondrial respiratory chain) that regulates the condition of redox in the molecule to boost the cell’s function. The chromophores have copper and heme centers that absorb light from the near-infrared spectrum. The photons emitted by light dissociate inhibitory nitric dioxide from the enzyme cytochrome c oxidase, which increases electron transport and the mitochondrial membrane power, thus increasing ATP production. The energy density ( joules[J]/cm 2) corresponds to the effectiveness of laser radiation. It is also accountable for controlling and “speeding up” the transport of electrons through the mitochondrial respiratory chain. 16

It is believed the World Association of Laser Therapy has determined that targeted tissues require an energy concentration of between 5 and 7J/cm 2 to trigger biological cell responses. 17 Several studies employing cold laser therapy for muscle and joint pain have demonstrated that the best therapeutic results of laser therapy can be achieved by using greater energies (i.e., the HILT) and administering additional laser treatments. 18,19 Huang and colleagues 20 further demonstrated that the positive effects of cold-laser therapy depend on the quantity of power (J) administered to the affected nerves and tissue.

Furthermore, HILT could exert a direct stimulatory impact on nerve structures that could enhance the speed of recovery from conduction block or inhibit A-delta or transmitting C-fibers. 21 Chow and Armati 22 revealed that animal studies with noxious stimuli show that HILT devices result in the nociceptor-specific inhibition of nerve conduction and can result in an impaired transmission of pain signaling from peripheral regions toward the central nerve system. Additionally, it is becoming clear that laser therapy could alter neuronal physiology, affecting the flow of axons and the cytoskeleton’s organization. The effects of laser therapy are entirely reversible, with no negative side consequences or damage to the nerves that linger.

In the end, the analgesia induced by lasers depends on the ability of infrared radiation to regulate different metabolic processes by converting the laser’s energy into photo-physical and biochemical approaches to transform the energy produced by lasers into and use it to boost cell healing. 21

Techniques Used for Administering Laser Therapy

Many factors affect the therapeutic effect of treatments using infrared light, including the energy intensity, frequency, laser delivery system, number of treatment sessions, and duration. 23 The absence of consistency in controlling these crucial variables is the reason for the inconsistent results in peer-reviewed research. There is also the suggestion that a therapeutic window exists to produce efficient photo-stimulation to reap the medicinal benefits of PBM treatments. 23 Other crucial questions that require further investigation include the evaluation of the effects that laser treatment has on the growth of cancerous cells that are abnormal when the therapy is employed to treat cancer-related pain, as well as the impact of the treatment with lasers on patients suffering from concussions as well as chronic neurodegenerative disorders.

The dosage of therapeutic lasers is based on three main factors: power output, wavelength, and duration (i.e., the length of treatments). 17 These aspects have also been proven to play the most significant role in improving the healing of tissues and enhancing clinical outcomes. 20,24-25 Surprisingly, the precise dose needed to create the desired effect of photo-stimulating on specific body areas remains unexplored. Finding a therapeutic quantity without over- or under-stimulating the patient’s tissues is among the most challenging aspects of applying PBM treatments. 25 If the amount of energy absorbed is insufficient to activate the tissues that absorb it and cause any changes or reactions, then no changes are likely to occur in the targeted tissues. The case of weak stimuli (i.e., overdosing or not doing enough) results in very little or no impact on the function of cells, while moderate to powerful laser stimuli improve the function of cells. In contrast, extreme stimuli (i.e., overdosing) may inhibit or block the part of cells and may further harm tissues because of the adverse effects of overheating tissues. 20 Future studies are required to determine the best dosages and frequency/duration of cold laser treatments treating chronic and acute pain, using each LLLT and HILT.

Wavelength is an important measure because it determines the capability of the laser beam to penetrate the tissue (Figure 1. and Table 4.). 26 If light therapy is applied directly to the skin of the patient and the skin is exposed, a portion of the light therapy effect of the laser is diminished by the superficial layers of tissue because of absorption into the skin’s pigments (e.g., melanin). Joensen et al. 27 discovered that the percentage of energy penetrating the skin is 20 percent for the wavelength of 810 nanometers and 58% for the 904 nm wavelength. Tuner and coworkers have examined the causes of negative research using LLLT. 28-31 For instance, the skin and subcutaneous tissues took up most of the energy (50 percent to 90 percent). According to the wavelength, only 10 percent to 50% of it gets into the tissue’s deeper layers.

Diodes with wavelengths ranging from 400-700 nm send light energy into the epidermal and subdermal skin layers (<1 millimeter) and therefore are ideal for treating superficial wounds and skin conditions. They can also cause burns when near the skin’s surface. Laser diodes with wavelengths ranging between 820 and 904 nm can transmit light energy 2 to 4 centimeters beyond the skin’s surface. Lasers with more extended frequencies (>1,000 nums) are the best to treat deep tissue injury (e.g., muscles ligaments, deep fascia, joints). 24,32-33

Contrary to LLLT, the HILT laser is applied in short bursts (120-150 milliseconds) or repeatedly at intervals of 60 seconds, with a concise duty cycle (0.1 percent) to stop the laser from reaching the threshold of the tissue while allowing it to allow sufficient temperature relaxation (Table 4.). This is crucial to prevent superficial tissue damage and potentially harmful thermal accumulation that can cause the tissue to be damaged due to excessive heat in your soft tissues. In addition, the pulsed distribution of light permits greater doses of energy to penetrate deep tissues, specifically when the pulses are short and have meager repetition rates. 34 For instance, a 905-nm continuous wave infrared laser permits 2.5 cm of penetration for the clinically-effective dose of energy from the photo, whereas an infrared super-pulsed laser of 905 nm can reach a depth of 10 cm in milliseconds. 34 However, using more extended frequencies (>1250 millimeters), the possibility is to give longer durations of pulses, all the way to the duration of a short continuous wave, which is 60-80 seconds, to allow for greater tissue penetration for a more significant long time frame which results in a more medical effect, but without causing tissue damage. Higher-power continuous emission that is longer-pulsed offers a broader coverage (i.e., more extensive treatment areas) and an enhanced photomechanical therapeutic effect. The more extensive range that comes with the latest, higher-powered HILT equipment also helps reduce the time required for treatment.

Laser therapy for cold is performed by using a straightforward “point and shoot” technique on the targeted tissue area(s) or nerves. Additionally, it can pinpoint the location of pain (by identifying the nerve’s innervation to the symptomatic region [i.e., peripheral nerve roots). The other crucial variables to consider when applying laser therapy include the most effective strength (W) and the wavelength (nm) for the light beam to ensure adequate tissue penetration and the treatment time, as well as the number of follow-up and initial sessions. The person administering the treatments should be certified in safe laser procedures and well-versed in anatomy, kinesiology, or physical therapy. Once the pain area is identified and identifying the location of pain, the laser beam will be directed directly at the skin at various distances based on the power and the wavelength of the laser device. Lasers with low power used to perform LLLT can be positioned directly on and within 3 to 5 inches of the skin’s surface. However, close contact between the head of the laser with the skin may cause cross-contamination between patients. In general, these superficial LLLT treatments last between 5 and 20 minutes.

However, the most potent HILT devices require that the probe be held between 10 and 12 inches from the skin’s surface to prevent overheating of the treated region. The targeted body area(s) are treated using an array of interspersed continuous 60-sec treatments that fill in the symptomatic area (the exact distance varies based on the size of the laser’s beam). In the current HILT systems, the size of the laser beam ranges between 2.5 to five centimeters. Limiting the treatment time of HILT between 60 and 80 seconds at each location will prevent overloading the tissues, leading to fatigue and the release of muscle enzymes.

Based on the extent of the affected region and the number of symptomatic body parts, A treatment session with HILT can be between 10 and 45 minutes. The patient may be asked to do simple exercises for range of motion before or during the laser treatment session if there is a joint or tendon to maximize the effectiveness of treatment. The pain relief following one treatment session lasts between 2 and four days. However, with repeated sessions, the effects could last for 7 to 10 days or even longer. Even though some acute injuries heal within a couple of sessions of treatment, most chronic pain disorders require an interval of between 8 and 12 sessions of therapy for 3 to 4 weeks and then maintenance treatments each 3 to 5 weeks for more advanced diseases. We have discovered that the effects of pain relief of HILT for patients suffering from chronic pain are comparable to those achieved by the use of needles on dermatomes or acupoints. 2 However, the intensity of the immediate response to HILT seems to be more potent than the effects of acustimulation. Additionally, the beneficial effect lasts longer.

Laser beams are directed at surgical incisions for after-operative analgesia (and to promote faster healing of wounds). Painful trigger points Acupoint sites that are which are associated with pain paraspinal region of the spine, the peripheral nerves that supply the areas of pain and numbness (e.g., the neuropathic pain), and broad tissue coverage that reduces inflammation and pain in a particular area by stimulating the healing process of peripheral nerves and tissues. 35 From a security standpoint, the most critical aspect is to prevent direct radiation of laser light to the eye, which could cause retina damage. Goggles with special protection should wear by the patients and the operator during treatments. They should block the radiation of the laser system that is being utilized and are available by laser safety companies (e.g., Laservision USA). Laser technicians should become certified for laser safety by completing an online course.

 

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