Posted on 13 April 2022
We recently wrote an article about the potential benefits of hyperbaric oxygen therapy (HBOT), a treatment in which the recipient breathes 100% oxygen in a pressurised chamber, usually to at least twice that of normal atmospheric pressure. HBOT has mainly been studied for its ability to accelerate healing for certain types of wound, namely those in which oxygen delivery to the site of injury is reduced. There is some early evidence that HBOT might benefit patients suffering from ‘long COVID’, a poorly understood condition in which people can experience a diverse range of symptoms (such as fatigue, shortness of breath and concentration problems) for many months following the initial infection. There is also preliminary evidence that HBOT may protect against age-related decline. You can read about this evidence and its caveats in the aforementioned article. The current article will briefly discuss whether the effectiveness of HBOT could be enhanced by another somewhat unusual therapy: low level laser therapy (LLLT), also called photobiomodulation (PBM).
PBM is the application of light, usually using a low-power, red or near-infrared light source (laser or LED), in order to promote tissue repair, reduce inflammation and relieve pain. PBM has been proposed to work by increasing the activity of enzymes in the mitochondria, the ‘cellular organs’ that convert nutrients into ATP, the universal cellular fuel. This results in the release of nitric oxide (an important molecule for blood vessel health), while increasing the production of ATP and reactive oxygen species or ROS (metabolic by-products that can damage other molecules, including DNA). A small increase in ROS may actually be a good thing, because together with a rise in ATP, this triggers the expression of genes that promote cellular repair. There is also some evidence that light-sensitive proteins on the surface of cells (called TRP channels) could be responsible for some of the effects of PBM. For example, lasers can trigger the release of histamines from immune cells.
In diseased tissues, PBM seems to reduce inflammation and lowers the production of reactive oxygen species or ROS. Multiple studies suggest that PBM is effective in promoting wound healing. In humans, these studies have mainly looked at slow-healing wounds such as diabetic wounds in which blood flow to the injury is restricted. This research has generally shown promising results, although larger trials are needed.
Studies have also looked at the effects of PBM on lung inflammation and found beneficial effects, though most of this research is limited to animal models. There’s recently been interest in whether PBM can be beneficial in treating acute lung inflammation in COVID-19 patients. While some studies have reported positive results, a systematic review concluded that more clinical trials are needed to properly answer this question. Much the same can be said of using PBM in the rehabilitation of patients with long COVID.
Since HBOT and PBM appear to have beneficial effects in many of the same health conditions, some scientists have asked whether the two therapies might complement each other. However, there’s currently very little research on this subject in humans. Studies have reported that PBM in addition to HBOT improves wound healing to a greater extent than HBOT alone in venous leg ulcers and Achilles tendon wounds. Both of these studies looked at topical hyperbaric oxygen – that is to say, the wound itself was exposed to oxygen at high pressures. It’s clear that more research into this kind of combination therapy is needed.
During ageing, our mitochondria become less efficient, which leads to a decline in the production of ATP and an increase in harmful reactive oxygen species. Many researchers suspect that this process, known as mitochondrial dysfunction, could be one of the key drivers of ageing process itself. Since PBM appears to improve mitochondrial health and activates protective genes, scientists have studied whether it can reduce signs of ageing, particularly in the brain (PBM can penetrate up to 3cm of bone). In this regard, there is some evidence that PBM may improve attention, memory and mood in older people, probably by improving mitochondrial, vascular and neuronal function. PBM also appears to prevent hyperactivity of the brain’s resident immune cells (the glial cells) and reduce inflammation, which may protect against neurodegenerative disease.
A number of clinical trials also support PBM as a method of skin rejuvenation. However, many of these trials are of poor quality, have small sample sizes, and often have conflicts of interest due to receiving funding from companies selling PBM therapies. It’s also not certain whether the weaker LED light sources that are often marketed as a skin treatment produce the same effects as the higher-powered lasers, which are what higher quality studies tend to use.
Photobiomodulation is a promising therapy that could complement HBOT in the treatment of multiple diseases, and may also have protective effects on the ageing brain. We need more, higher quality clinical trials to study PBM, especially in combination with HBOT, to confirm its effectiveness.
Mechanisms and applications of the anti-inflammatory effects of photobiomodulation: https://dx.doi.org/10.3934%2Fbiophy.2017.3.337
Treatment of diabetic foot ulcers in a frail population with severe co-morbidities using at-home photobiomodulation laser therapy: a double-blind, randomized, sham-controlled pilot clinical study: https://doi.org/10.1007/s10103-021-03335-9
Low-level Light Therapy for Treatment of Diabetic Foot Ulcer: A Review of Clinical Experiences: https://pubmed.ncbi.nlm.nih.gov/27391634/
Photobiomodulation Therapy as a Possible New Approach in COVID-19: A Systematic Review: https://dx.doi.org/10.3390%2Flife11060580
Conservative Management of Achilles Tendon Wounds: Results of a Retrospective Study: https://www.hmpgloballearningnetwork.com/site/wmp/content/conservative-management-achilles-tendon-wounds-results-retrospective-study
Comparison of the efficacy of topical hyperbaric oxygen therapy alone vs a combination of physical methods including topical hyperbaric oxygen therapy, magnetotherapy, and low-energy light therapy in the treatment of venous leg ulcers: https://doi.org/10.1111/dth.14474
Photobiomodulation for the aging brain: https://doi.org/10.1016/j.arr.2021.101415
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