Sessions, called dives, last around two hours daily, with two ten-minute oxygen breaks to prevent oxygen seizures.
“Dive” is the word used in hyperbaric medicine for a session, because the pressures involved are described in the same terms as depth underwater. Each additional atmosphere of pressure is equal to 33 feet of depth of seawater.
So two hours, daily, is the shape of the commitment. The daily part matters as much as the two hours if you’re arranging transportation or time off work.
The oxygen breaks during the session are not there for comfort. They are there to prevent oxygen seizures, which are among the more serious hazards of the therapy.
On the pressure itself, sessions usually go to 2.4 atmospheres at 100% oxygen. Hyperbaric oxygen therapy means placing a patient in a pressurized chamber of up to 3 atmospheres. Put simply, the air pressure inside the chamber is about two and a half times greater than the normal pressure in the atmosphere.
How many sessions is a separate question. A typical course is 33 sessions, which can be extended if needed.
Protocols differ by condition. Hyperbaric dives follow specific proven dive protocols depending on the condition being treated, so these figures describe what’s usual, not necessarily your own course.