LASERS IN HEALTHCARE – Overview and focus on Photobiomodulation Therapy

[Originally published in Podiatry Review Autumn Issue 2022, 79(4) pp 36-39’]

Introduction

Historically light has been used as medicine for thousands of years with the ancient Greeks, Romans and Indians utilising the power of natural sunlight. Light therapy is used in a variety of ways to either treat or destroy tissues in the body. There are now lasers for hair removal, surgical cutting, ablation, tattoo removal and tissue healing amongst many other uses.

The word laser is an acronym for ‘Light Amplification by Stimulated Emission of Radiation’, describing an optical device that produces an intense, monochromatic, coherent beam of light. The worlds first laser was built and patented in 1960 by the physician Theodore Maiman. In 1967 Endre Mester discovered photobiomodulation (PBM) whilst attempting to cure tumours in rats but instead noted an increase in hair growth and healing times.

Lasers of numerous types are now present in clinics, hospitals and medical centres across the globe. This article will focus primarily on PBM

Principles of Medical and Therapeutic Laser Mechanisms

Laser therapy, also called Photobiomodulation therapy (PMBT) works by delivering light to tissues where it interacts via one or a combination of biological effects. These include photothermal (heat delivery), photochemical (alterations to chemical processes), and photomechanical (non-destructive distortion of cells). Some lasers, used for removal of tissue, rely heavily on the photothermal effect to cause tissue ablation. However most of the research in PBMT has concentrated on the photochemical effect

The photochemical effect relies on photoreceptors within cells and tissue (also known as chromophores) absorbing light and triggering a cellular response (Sutherland, 2002) and subsequent physiological changes. Research has demonstrated several photochemical effects at cellular and molecular levels. The most widely reported effects include: effects on cellular metabolism, ATP production, and mitochondrial membrane potential (Bayat et al 2005, Monici et al 2013). The absorption of light by chromophores such as cytochrome c oxidase affects production of reactive oxygen species and nitrous oxide, leading to an increase in ATP production (Hamblin, 2017) and modulation of the inflammatory response – reducing inflammation, improving cellular metabolism and increasing the natural healing response of the body. PMBT can reduce the permeability of mitochondrial membranes leading to lowering of the action potential and reduced speed of neural transmissions contributing to an analgesic effect [Chow, David and Armati, 2007].

There are a large number of suggested additional cellular and molecular effects of PBM, with research continuing to reveal new mechanisms and further explore existing knowledge [Hamblin and Liebert, 2022].

Properties of laser and their importance

Wavelength

Laser light is monochromatic which means it consists of a single wavelength. This enables lasers to be designed and used for a specific function. Wavelength is the primary factor in determining where the light is absorbed and therefore how well it can penetrate into tissue. The depth to which the light penetrates and its subsequent ability to reach the target area is key to carrying out effective treatments

The wavelengths of light used in PBMT have different absorption rates by the various chromophores that exist in tissue. There are certain chromophores (namely H2O, haemoglobin and melanin) that exist in high concentrations in superficial tissue and can absorb these wavelengths of light and therefore reduce the penetrating ability of the beam. By selecting a wavelength that is absorbed least by these chromophores, the % of light which reaches the target tissue can be maximised.

In photobiomodulation therapy (PBMT) the ‘therapeutic window’ is often referenced. This is an absorption spectrum of wavelengths covering from approximately 600nm up to 1200nm. The specific wavelength selected will depend on the depth of penetration required for the desired clinical outcome of the device.

Additional Parameters For Consideration

Whilst wavelength is a key factor in laser treatment, there are other important parameters to consider. These include energy density (Jcm2), power (W), spot size, pulse frequency (Hz) and treatment protocol.

The energy density or dosage, measured in Jcm2, is important in determining the cellular effects of the treatment. Dosage is calculated by Energy Density (J/cm2) = Power Density (W/cm2) x Time (s). Taking into consideration the Arndt-Schultz graph of photobiological stimulation it can be deduced that there is a peak dosage to stimulate cellular activity and that higher dosages may inhibit rather than stimulate (Sommer et al 2001).

Many therapeutic lasers deliver pulsed waves at varying frequencies. Pulse rate can influence the cellular response achieved. Pulsed wave is reported to be more effective for healing, analgesia by enhancing ATP synthesis in mitochondria (effective range between 10 and 8k Hz) with specific cellular effects at specific frequencies (Kim et al 2017).

Because the most effective treatment outcomes for specific conditions are based on a number of key parameters and many of these vary greatly between devices, laser companies often have integral pre-set parameters or a guide to suggested settings with their equipment to allow practitioners to get the best results from that particular machine. These settings can then be adjusted as required to allow for customised treatments for individuals.

PBMT has a cumulative effect with each treatment building upon the effects of the last. For this reason, it is important to carry out a course of treatment at regular intervals with most manufacturers suggesting that treatments be carried out at a rate of a minimum one per week, with 2-3 sessions weekly often suggested.

Laser classification and nomenclure

Lasers are classified for safety purposes with 4 main classes and a number of subclasses. Most lasers used in healthcare are class 3B or class 4 devices

Laser classification sources:
https://www.gov.uk/government/publications/laser-radiation-safety-advice/laser-radiation-safety-advice
https://warwick.ac.uk/services/healthsafetywellbeing/guidance/lasers/appendix1classification

There have been over 70 different terms used to describe the use of near infra red light to cause change in tissues with some referring to specific classifications. Some of the more common terms are listed here:

In addition to the varying nomenclature and classification of laser there are also different types of laser devices with specific applications for each.

Safe use of laser

It is important for practitioners to understand the safety implications of laser and how to ensure their practice is safe for them and their patients. As noted in the laser classification table, class 3 and 4 lasers are potentially harmful to eyes and skin, and must therefore be used in a careful and controlled manner. The light you can see being emitted from some therapeutic lasers is a guide light as opposed to the actual functional wavelength which may be invisible to the naked eye. Optical harm can occur even though the light cannot be seen or felt until it is too late

Points for consideration for safe operation include controlled access to rooms where laser is being used, window coverings, reflective surfaces in the room, warning signs on doors, flammable chemicals in the vicinity of the laser equipment and knowing the optical hazard zone of your laser. The MHRA (2015) document suggest daily, weekly and annual/bi annual checks and tasks which can be carried out such as checking condition of eyewear and the functionality of warning lights etc.

Each clinic using laser should appoint a Laser Protection Officer (LPO) who is a nominated person, usually a member of staff, who is responsible for ensuring health and safety standards are being met. For additional help, a Laser Protection Adviser (LPA) can be employed to help a clinic ensure risk assessments have been properly completed and that all guidelines and standards are being met

THERAPY LASERS: Indications for use

The primary effect of PBMT is to reduce pain, inflammation and swelling and to encourage the healing process (Bayat et al 2005, Monici et al 2013). Therefore, the number of potential applications is huge. Currently there is strong evidence for the use of laser to treat musculoskeletal (MSK) pain in both chronic and acute and to aid in muscle recovery, stamina and strength. The NICE guidelines already recommend PBMT for the treatment of oral mucositis. There is also evidence to suggest PBMT is
an appropriate treatment for wounds, in cases of lymphedema and neuropathies. There is ongoing research at the Limburg Oncological Laser Institute looking into the use of laser as both a preventative and a treatment for post-operative cancer care for issues including lymphedema and chemotherapy induced peripheral neuropathy as well as other undesirable side effects.

Podiatric use of PBMT is most commonly in wound care and for MSK conditions such as tendinopathies, plantar fasciitis, haematomas, bursitis and arthropathies. There are specific devices on the market for the treatment of fungal nail infection and verrucae.

When using PBMT as a treatment in MSK patients in particular, it is important to note that the laser forms part of an overall treatment plan. A full and proper assessment is essential to allow an accurate diagnosis and appropriate adjacent treatment interventions which will ensure the root cause of the issue is also addressed. The function of PBMT in these cases is primarily to rapidly reduce pain and inflammation to allow the patient to carry out any rehabilitation exercises and to return to activity as quickly as possible.

Adding value in Private Practice with Therapeutic Laser

Investing in equipment can be daunting and clinic owners need to know that it will be worth their while. Adding therapeutic laser to the range of treatment options could add value for patients, practice and practitioners.

Value For Practices

Adding a laser to your clinic has potential to bring value to a clinic in a number of ways:

• It could open up a wider selection of patients. It may allow clinicians to offer treatments for conditions which they currently do not treat such, as arthropathies, attracting new patients as a result.
• It aids clinics in standing when compared to competitors. Patients may choose to visit due to the option of laser therapy when others in the vicinity do not offer it.
• It can generate word of mouth referrals.
• It allows clinicians to offer treatment to those patients who have tried many other interventions.
• Introducing laser into your clinic gives you great potential to make a return on your investment.

Please see the examples below:

Value For Patients

Feedback is generally that patients love laser therapy. Some reasons are:

• It is generally painless.
• It could speed up recovery time.
• It could reduce discomfort quickly therefore makes rehabilitation easier.
• Patients love tech! A laser treatment appeals to many patients and gives them a story to tell their friends.
• Extremely low risk of side effects.

Value for Practitioners

Introducing laser can make daily practice more enjoyable. It may help clinicians to: 

• Attract a new type of patient. For example, it may encourage more athletes or MSK patients to a clinic.
• Save hard worked hands! Many manual therapists have described how they use the laser to soften/ relax tissue to “save” their hands and allow manual work.
• Great feedback from patients gives a feel good factor. Clinicians do what they do to help people and there’s nothing more satisfying that hearing that patient to achieve their treatment goals.

SUMMARY

Light as a therapy has been utilised for hundreds of years and its potential continues to be recognised and researched. In Podiatry there is a huge scope for therapeutic laser covering MSK conditions, wound care and more. Excellent clinical skills, an accurate diagnosis and implementation of appropriate treatment plans alongside a full understanding of treatment parameters and appropriate dosage is important so as to achieve the best possible treatment outcomes. Proper training to ensure safe and
effective use of laser devices is paramount. Adding laser into private practice can add a variety of benefits for patients, practitioners and for the business itself. The use of light in healthcare, specifically in the field of photobiomodulation is a hugely exciting area to be involved in as indications for use and the research into its efficacy continues to grow.