Chronic pain constitutes a special therapeutic challenge. We present a narrative review of the role of hyperbaric oxygenation(HBOT) treatment in the treatment of neuropathic pain, and its applications in chronic pain, dysfunctional neuro sensitive syndromes, and oncological pain. The knowledge of HBOT indications in algiology and its application in medical practice can contribute to improving the patient’s quality of life.

The objective of this narrative review is to conduct a bibliographic search of the mechanism by which HBOT has an action on neuropathic pain and the applications of hyperbaric oxygenation therapy in the treatment of pain. The bibliographic search of the works published until 2019was carried out in MEDLINE EMBASE, BIREME, Lilacs, Scielo and Cochrane library.

Hyperbaric oxygen decreases neuropathic pain by acting directly on neuronal tissue by several mechanisms: it induces mitophagy(degradation of damaged or aged mitochondria), decreases neuronal inflammation mediated by astrocytes, and decreases the expression of nitric oxide synthetase enzyme (nNOS) neuronal and inducible nitric oxide synthetase (iNOS).

Due to its mechanism of action and its activity to reduce neuropathic pain by contributing to the improvement of mitochondrial functionalism, all pain related to inflammation, neuropathy or nociceptive pain in wounds can be lessened with hyperbaric oxygenation treatment.

A special item is pain related to cancer treatment (chemotherapy or radiotherapy), where hyperbaric oxygen was shown to reduce the inflammation associated with radiation and contribute to the decrease of neuropathic pain related to chemotherapeutic agents. Several pain studies conducted on the intensity of pain in patients with fibromyalgia showed that one of the mechanisms by which pain decreases in this pathology is the decrease of nitric oxide synthetase inducible with hyperbaric oxygen.

HBOT reduces cerebral blood flow, in addition to contributing to the decrease in muscle hypoxia at tender pain points, and decreases interleukin 1 and TNF-α. Hyperbaric oxygen significantly reduces pain points in treated patients compared to those who do not receive treatment: from17.5 points (from 19) to 5, in some cases with very good response. In measurements, through the pain meter, an increase in pain tolerance was found in the sensitive points and in other points of the body granting an increase in pain resistance.

It is also shown that HBOT is effective in reducing pain in complex regional pain syndrome (CRPS), where it is thought that there is an excessive activity in the sympathetic nervous system. With HBOT, hyperoxia contributes to vasoconstriction, decreasing edema and increasing partial oxygen pressure. The pain can decrease even in the first session and with a series of 20 to 30 sessions it decreases progressively.

In rheumatic diseases, HBOT has an anti-inflammatory analgesic effect because it decreases inflammation, and is also seen in patients with a rheumatic disease such as arthritis and mainly in primary and secondary vasculitis.

Pain is one of the common symptoms in patients with head and neck cancer. 50% of these show pain before starting treatment,81% during treatment, 70% at the end of treatment and 36% complain of pain up to6 months after treatment. HBOT was shown to significantly reduce (90%) pain in those with advanced prostate adenocarcinoma when combined with estrogen treatment.

When HBOT is used in the treatment of injuries related to EVP, the relief of ischemic leg pain is frequently observed. While many of these patients require vascular surgery, hyperbaric oxygen can relieve pain before the procedure and also engage in the acute post-surgical process to decrease inflammation. It has been proposed that, in EVP, HBOT decreases hypoxia and edema, decreasing the accumulation of allogeneic polypeptides and increasing endorphin receptor sites.

The incorporation of HBOT into the therapeutic scheme of chronic ulcer cure not only allows healing in lesions refractory to treatment but also improves the quality of life and significantly reduces pain during healing because it reduces inflammation and promotes regenerationAxonal wounds contributing to the decrease of neuropathy and neuropathic pain.

Hyperbaric oxygenation treatment should be considered in any pathology in which pain is an added symptom and, even more, if it is chronic since it has a direct activity on neuropathic pain. In addition to being useful in the treatment of neuro sensitive syndromes, it can be incorporated into the treatment for oncological pain in EVP, autoimmune and rheumatologic diseases with an inflammatory component, chronic wounds, spinal injuries, lumbar pains and even pain in post-stroke syndrome and brain trauma. Possible surgical interventions should be included as much as possible because, in addition to promoting healing and reducing infections, hyperbaric oxygenation produces analgesia, reduces inflammation and improves the quality of life in the immediate postoperative period.

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Reference

Ramallo, L; Verdini, F; y Jordá-Vargas, L. (2019). Terapia de oxigenación hiperbárica en el tratamiento del dolor. Revista del Hospital Italiano, Vol 39, Nº 3.