Fibromyalgia is a multifactorial syndrome characterized by widespread musculoskeletal pain, fatigue, sleep disturbances, morning stiffness, loss of functional capacity, mood alterations, as well as a decline in memory, cognition, headaches and a myriad of other visceral and cognitive maladies (1,2). These symptoms negatively affect the quality of life of patients. Fibromyalgia is diagnosed using the criteria proposed by the American College of Rheumatology. In 2016, the latest revision of these criteria re-established the importance of generalized pain as the main symptom (3), but also considered other symptoms equally as important for the diagnosis considering these criteria. The estimated global population affected by this disease ranges between 0.5-5.8% (4), and the disease particularly affects women (2.4-6.8%) (5). Fibromyalgia is a disabling syndrome with no effective pharmacological cure; thus, recent alternative therapeutic strategies have been proposed to mitigate pain and fatigue, and avoid the side-effects of polypharmacy (6).

Chronic musculoskeletal pain has a worldwide prevalence of ~30% (4). Managing the unpleasant sensory and emotional experience associated with tissue damage by patients with chronic pain is a difficult predicament that requires a multidisciplinary approach, particularly in patients suffering from fibromyalgia, in whom the control system that interprets and distinguishes painful stimuli is overly sensitive (7). Its treatment is based on the combination of pharmacological and non-pharmacological approaches and interventional techniques, which usually only achieve modest results in pain relief; in this regard, the absence of positive results or the generation of adverse effects can be the reason to stop treatment (7). Furthermore, pain and fatigue are frequently associated with comorbidities, such as sleep disturbances, depression and metabolic syndrome, which render treatment difficult (7). Obesity is an increasingly prevalent health concern in the Mexican population; thus, the risk of comorbidities associated with metabolic deficiencies and fibromyalgia can increase progressively. In this regard, the amelioration of pain and fatigue by an effective therapy can allow the opportunity for obese patients with fibromyalgia to lose weight by controlling physical activity to avoid chronic comorbidities. The greater the physical and mental deterioration caused by comorbidities, the more difficult it is to identify effective personalized treatment (7,8).

Among non-pharmacological alternatives for the treatment of fibromyalgia, hyperbaric oxygen therapy (HBOT) has been proposed as a novel effective therapy; however, further studies are required in populations with different genetic, ethnic and cultural traits to verify its effectiveness (8-10). Although HBOT was initially designed to treat diving-related injuries, promising results have been observed as a nociceptive, inflammatory and neuropathic pain analgesic (7). HBOT is a treatment providing 100% oxygen at a pressure above one atmosphere absolute (ATA). The main mechanisms of action activated by HBOT to reduce pain can be reversed by hypoxia in dysfunctional tissues by increasing the partial pressure of arterial oxygen (7-10). In addition, it can exert hydrostatic pressure to stimulate elimination of inert gas from tissues (11).

The present study aimed to determine whether HBOT is effective in treating pain and fatigue, as well as improving the quality of life and reducing the number of drugs used by patients diagnosed with fibromyalgia in a Mexican population.

The patient population participating in the present study was predominantly married active professional women, <55 years of age, whose BMI corresponded to being overweight or obese. One fifth of the patients were diagnosed with secondary fibromyalgia, which implies comorbidities, such as stroke, mood disorders or diabetes (10). The baseline perception in this subgroup comprised high levels of pain intensity (VAS scores between 8 and 9) and fatigue (FATIC-F between 42-52), suggesting that these women cope with severe levels of pain and fatigue daily (10,14). Previous studies have reported a close association between chronic pain intensity or fatigue and high BMI (14-17), which may explain the results of the present study.

The effectiveness of HBOT to treat Mexican women with fibromyalgia, who were overweight or obese, was evaluated in the present study by measuring perceived pain, fatigue, quality of life, as well as the number of drugs used. A previous study reported that a 50-year-old Turkish woman, with a mean BMI of 29 kg/m², had VAS and FIQ scores similar to those reported in the present study (8 and 73, respectively) (18). Neural therapy consisting of intracutaneous 1% lidocaine administered as a local anesthetic into painful points was used to treat fibromyalgia in this study, and the posttreatment scores were 3.7 (VAS) and 40 (FIQ) (18). In another study, Korean women (mean age, 47 years) with a VAS score of 8.8 and FIQ score of 80 were treated with transcranial direct current stimulation; the treatment reversed perceived pain to 6 (VAS score) and decreased the FIQ score to 70(19). Notably, no significant differences in VAS or FIQ scores were observed in Spanish women (mean age, 53 years) treated with low-intensity physical activity programs for 12 weeks (20); however, a moderate-intense aerobic exercise program effectively reduced pain to 5.7 and the FIQ score to 55(21). In Israel, a group of women (mean age, 50 years), with an average BMI of 27, were treated with HBOT (22). In addition, Turkish women (mean age, 40 years) also treated with 15 sessions of HBOT exhibited reduced VAS scores, from 64 to 31. Collectively, these reports suggest that non-pharmacological approaches are effective in reducing the severity of fibromyalgia symptoms.

Health must be perceived as a daily mutual commitment by subjects and institutions to favor physical, psycho-emotional and social wellbeing. Patients must be mindful of their eating habits and fibromyalgia treatment needs to be holistic. Thus, therapeutic management should be characterized by integrated and multidisciplinary interventions that ameliorate physical complications but also address the psychological and social aspects of the disease (23). Pain is one of the main inhibitors of patients' adherence to controlled physical activity programs (24). In addition, activity is necessary to lose weight, as being overweight or obese increases the risk of severe pain. A variety of drugs, such as muscle relaxants, analgesics, anti-inflammatories, antidepressants and anticonvulsants have been widely used as pharmacological therapy for fibromyalgia (25). A common side-effect of polypharmacy is the development of metabolic or mental health issues, aggravating patients' conditions and severely impairing their quality of life (23). Thus, HBOT may be a suitable approach to dissociate the negative feedback loop between high BMI-pain-sedentarism to implement a multidisciplinary management program to treat overweight or obese patients with fibromyalgia.

In conclusion, HBOT in patients with fibromyalgia significantly improves pain and fatigue management, as well as other aspects of the disease, such as the quality of life and the possibility to avoid the side-effects of polypharmacy. However, further studies are required to establish a standardized treatment scheme with HBOT, not only in fibromyalgia, but also in other chronic disorders in which widespread pain is a symptom that generates inability. Taken together, the results of the present study support the hypothesis that this procedure can be used as an effective adjuvant to contribute to the wellbeing of female patients that suffer from fibromyalgia. Reduction of pain and fatigue in overweight or obese patients opens the opportunity to initiate an increment in physical activity and exercise to lose weight and decrease the risk of health-associated chronic degenerative comorbidities.