Stephany,
I had an open wound on my jawline for over a year. My skin was so damaged by the radiation that it just gave up. After several courses of antibiotics, the plastic surgeon on my team decided to patch the hole and replace some of the thin skin with a forearm flap. As is usual, he left a drain to let excess fluids escape after the surgery. The drain hole wouldn't heal, so I hadn't gained any ground.
After HBO treatments, I had a very minor 1-hour surgery to clean out the wound and close it up. It healed. HBO worked for me. I don't know if it would help your mom.
You asked about the treatment, and Brian pointed you to the many good articles on the OCF site. Let me just add that I traveled to the HBO center every day for 40 days. After changing into scrubs, I sat in a steel tank for 2 hours with up to 3 other patients and an HBO technician. I played cards, read books, and chatted with my companions.
Once in the tank, I put on a light weight "helmet." The technicians increased the pressure I the tank to about 2.5 times normal atmospheric pressure. Then, they pumped pure oxygen into the helmet.
There were only a couple of side effects. I got nearsignted gradually and it has taken a couple months to get back to normal. And, I felt a little tired after the treatments.
There you have it. I hope this helps.
Ken