Rationale for PBMT(LLLT) to Treat COVID-19

It has also been established that PBMT reduces lung inflammation in experimental models, including LPS-induced pulmonary inflammation in mice [77] and rats [78], and in mice submitted to cigarette smoke to mimic chronic obstructive pulmonary disease (COPD) [79]. Several small-scale, peer-reviewed studies report the benefits of PBMT on respiratory disorders in human patients, including asthma [80] and COPD [81]. Shorter recovery times, less medication reliance, fewer respiratory symptoms, and improved radiological, immunological, and blood markers are all positive outcomes of PBMT seen in these patients [22].

The first major clinical trial of PBMT for COVID-19 patients was carried out by Vetrici et al. [22]. Despite the low sample size, the study demonstrated that adjunctive PBMT improved the clinical status of COVID-19 pneumonia above standard medical care. PBMT (808 nm and 905 nm) applied to the lungs increased peripheral oxygen saturation, relieved pulmonary symptoms, and improved chest X-ray findings. This suggests that PBMT could be used to improve COVID-19 patients’ respiratory and clinical conditions, decreasing the requirement for ventilator support and ICU stay. Similarly, a placebo-controlled trial of thirty severe COVID-19 patients found that, whilst the length of ICU stay did not change between groups, patients treated with 905/633/850 nm PBMT-sMF (PBMT combined with static magnetic field) showed reduced diaphragm atrophy and improved ventilatory parameters and lymphocyte count [82]. A case report by Sigman et al. (2020) used a combination of 808 and 905 nm PBM to treat a 57-year-old man with a severe case of COVID-19 pneumonia. The patient’s radiological findings, respiratory rates and oxygen requirements improved significantly after treatment, with no need for the predicted ventilator treatment [83]. These clinical reports all support the use of PBMT to treat COVID-19 and reduce the pressure on health services.

Up to now, most studies in the field of PBMT have focused on 600–700 nm and 780–850 nm wavelengths, but irradiation by 1060–1080 nm light has shown significant behavioural effects including cognitive enhancement [84,85] and executive functions [86], and so would be worth investigating for the neurological, as well as immune, features of COVID-19. The next sections (5.1–5.5) explore the rationale for these longer wavelengths of PBMT to treat COVID-19.