I've had HBOT to help with another infective problem, which was covered by the state government here in Australia. They always said they didn't work with autoimmune conditions directly though, not sure if there have been any studies since though, it is an interesting one..
It worked great for the infection and to help bone recover post surgery, but no obvious impact on the IBD, though things were fairly good at the time anyway
I never heard of this and needed to google it. You learn something new every day. I'd be interested to hear if anyone had this for an abscess and if it helped.