Hyperbaric oxygen treatment (HBOT), a procedure that involves increasing the oxygen supply in the blood to speed up the healing process, could be a safe and effective treatment option for people with fistulizing Crohn’s disease, according to an abstract presented at the Crohn’s & Colitis Congress, held January 19 to 21 in Denver. The study has not been published in a peer-reviewed journal.

For the treatment, patients go into a special chamber that creates a pressurized environment filled with pure oxygen, which is intended to fill the blood and repair tissues. HBOT encourages new blood vessels to grow and decreases inflammation and swelling. Inflammation can deprive cells of oxygen (hypoxia), causing tissue to die. (In turn, research has shown hypoxia can induce inflammation — so it can become a vicious cycle.)

“The decreased level of oxygen (hypoxia) and the development of inflammation are described to be two sides of the same coin; they can lead to each other,” says Sara Mesilhy, MBBS, a gastroenterologist with the Royal College of Physicians UK, who was not involved in the study. “Inflammatory products increase in cells with low oxygen. Inflamed tissue becomes hypoxic as a result of increases in their metabolic demands.”

Because HBOT is effective in treating conditions related to hypoxia, doctors have found that the therapy can be beneficial for people with Crohn’s (a common type of inflammatory bowel disease) who have difficult-to-treat and recurrent fistulas.

Hypoxia can contribute to inflammation in Crohn’s, which then can cause the formation of fistulas, small tunnels within the walls of the intestine that can connect to other organs or to the skin surface, causing pain and infection. The presence of fistulas means that inflammation has penetrated into adjacent organs, tissue, or skin.

“Hyperbaric oxygen therapy is a way to push oxygen into the colon through its tiny blood vessels,” said Parambir Dulai, MD, a gastroenterologist at Northwestern Memorial Hospital in Chicago, referring to a study published in April 2022 in which he and his colleagues looked at the benefits of HBOT for ulcerative colitis, another type of inflammatory bowel disease (IBD). “This kills the inflammation-causing bad bacteria that thrive in these low-oxygen environments. It resets the immune system and allows the colon to heal,” Dr. Dulai said.

To get a more comprehensive view of the effectiveness of hyperbaric therapy on Crohn’s fistulas for the new study, Amr Dokmak, MD, an internal medicine specialist with Catholic Medical Center in Manchester, New Hampshire, and collaborators reviewed 16 studies with 164 Crohn’s patients with fistulas who underwent 5,125 HBOT sessions.

Their analysis revealed that patients who received hyperbaric oxygen therapy had an overall clinical response rate of 87 percent. A total of 135 out of 164 patients had a clinical response. The definition of “clinical response” varies from study to study, but it generally means there has been significant improvement. For example, a study in the August 2021 Journal of Crohn’s and Colitis defined clinical response for a patient as “closure of at least 50 percent of fistulas.”

When looking at clinical response for specific types of fistulas, the scientists observed an 89 percent response for perianal fistulas (tunnels that develop between the inside of the anus and the outside skin near the anus) and an 84 percent response for enterocutaneous fistulas (an abnormal connection that develops between the intestinal tract or stomach and the skin).

“The response rate mentioned is considered very impressive, making it a promising approach,” says Dr. Mesilhy. According to UChicagoMedicine, advances have been made in IBD fistula healing through therapeutics such as biologics, and Mesilhy suggests that HBOT may prove to be an effective addition to the primary or initial therapy.

The findings on the perianal fistulas were based on 15 studies showing clinical response in 115 out of 130 patients diagnosed with this condition; for enterocutaneous fistulas, the clinical response was noted in 21 out of 25 patients from five studies.

Dr. Dokmak and his team noted that rectovaginal fistulas (connections that should not exist between the lower part of the rectum or anus and the vagina) were the fistula subtype least responsive to hyperbaric therapy, demonstrating a 29 percent response. Researchers noted response in 4 of 14 cases in five studies.

The rate of clinical remission, or closure of fistulas and absence of any draining, was found to be 59 percent, based on pooled data. Remission was noted in 85 out of 143 patients in 14 studies.

The authors concluded that randomized control trials are needed to substantiate the benefit of HBOT in fistulizing Crohn’s disease.

“The beneficial effects of hyperbaric oxygen therapy on inflammatory bowel disease activity may be not only due to increased oxygenation, but also to other changes the therapy makes as it adjusts the immune system by enhancing immune cells that protect the tissue, and enhances genes that produce intestinal barrier–protective elements,” says Mesilhy. “The exact long-term effects are still not known, as it varies from one patient to another — further studies are needed to evaluate the long-term effects.”

Treatment Can Be Pricey

HBOT has existed since 1834, when it was used to treat pulmonary (lung) conditions. Since that time, the therapy has been used for carbon monoxide poisoning, gangrene, wounds that won’t heal, and infections in which tissues are starved for oxygen, according to Johns Hopkins Medicine.

One of the major drawbacks of the treatment is its high cost, according to a review published in the International Journal of General Medicine in 2021.

“For effective treatment results, there is a need for 20 to 40 sessions of therapy, and one session usually costs $300 in private clinics and about $2,000 in hospitals,” noted the researchers.

Mesilhy adds, “There is a need for multiple sessions of therapy, so the treatment may not be affordable for all.”