Hyperbaric Oxygen Therapy for Perianal Fistulizing Crohn's Disease Not Responsive or Intolerant to Conventional Care: HYPNOTIC Pilot Study

Hyperbaric oxygen therapy (HBOT) is an effective intervention for improving healing of chronic wounds. HBOT involves the delivery of 100% oxygen in a pressurized environment, typically two to three times standard atmospheric pressure at sea level (2.0-2.5 ATA). This results in increased oxygen tension in plasma and promotes the diffusion of oxygen into tissue, which stimulates tissue restorative pathways that are essential for wound healing16. Hyperoxia also modulates the immune system by suppressing proinflammatory cytokines and promoting the production of anti-inflammatory cytokines. It also enhances the production of growth factors, mobilize stem cells, and stimulates anti-microbial pathways, all of which are believed to be central mechanisms involved in the repair of damaged tissue in IBD. The safety profile of HBOT is also excellent, with a reported adverse event incidence of 10 per 10,000. The most reported adverse event is middle ear barotrauma, which is minor and not life threatening. There is emerging evidence that HBOT may be an effective treatment option for perianal Crohn's disease (PCD). To date, 10 observational studies with a total of 118 patients with PCD refractory to conventional therapy have assessed the effectiveness and safety of HBOT (McCurdy et al., IBDJ 2021). In this small number of patients, HBOT resulted in high rates of clinical response (75% \[95% CI, 66%-83%; I2, 0\]) and clinical remission (55% \[95% CI, 44%-65%; I2, 61\]) (Figure 1). Additionally, the HOT-TOPICs study, an open-label observational study demonstrated that HBOT was associated with radiologic improvement of fistula tracts as shown by a reduction in the modified Van Assche MRI score from 9.2 (95% CI, 7.3-11.2) to 7.3 (95% CI, 6.9-9.7). Despite these encouraging results, formal controlled clinical trials have not yet been conducted in patients with PCD to determine the true clinical impact of HBOT in this disease.