Rochester, Minnesota - When Dave Boyett woke up after an operation to try to halt an out-of-control infection in his foot, what he saw brought him to tears – in a good way. "I looked down there, and it was all bandaged up. My foot was still attached, and it was a huge [relief]. And, yeah, I started to cry right there. I was so thankful."

Boyett's surgeon had prepared him for the possibility that amputation might be necessary. But, in the weeks leading up to the surgery, his doctors had sent him to more than two dozen therapy sessions in a hyperbaric chamber. "In its simplest form, hyperbaric therapy, or hyperbaric oxygen therapy, is breathing oxygen at a higher pressure than [our normal] atmosphere," says Dr. Paul Claus, the medical director for Mayo Clinic's Hyperbaric and Altitude Medicine Program.

Because of the technology's origins, each hyperbaric therapy session is called a dive. "It came out of [deep-sea] diving experience, when oxygen was used to decompress divers who had been too deep too long and absorbed too much nitrogen," says Dr. Claus. Today, it's used to treat many medical conditions, including diabetic wounds, gas embolisms, radiation injuries from cancer treatments and carbon monoxide poisoning.

Mayo Clinic's two triple-lock hyperbaric chambers are big enough to hold up to 12 patients who breathe pure oxygen. They're pressurized up to three times the atmosphere at sea level. Why? "They’re laws of physics, and, when you increase the pressure, you dissolve more molecules of oxygen in a fluid state," explains Dr. Claus. "It triggers the body’s response to produce new structure, new blood vessels, new connective tissue and to promote healing."

"It healed me really well – and quickly – and I was very, very pleased with it," says Boyett, who was battling chronic, diabetes-related wounds. He had already lost part of his foot. "He was at risk of having to need a revision of that amputation and lose the lower part of his leg," says Dr. Claus.

Improved blood vessel growth from hyperbaric oxygen therapy is credited with helping Boyett heal. The new blood vessels also carry more immune-boosting cells according to Dr. Claus. "It helps the white blood cells work more efficiently in those areas that are without adequate circulation, and, so, it helps fight infection."

There are about 2500 multiplace hyperbaric oxygen facilities in the U.S., but only a few dozen have the critical care capacity of the program at Mayo Clinic.