Hi Diana,
I a little experience of both HBOT and also Alzheimer's but not the two together.
It strikes me that for an Advanced Alzheimer's patient the experience of being pressurized might be difficult or even frightening. It might be difficult to get the patient to appriciate the reasons for doing the treatment and they might not want to do it. If a patient suddenly wanted to stop the treatment there would be the difficulty of depressurizing, so they wouldn't be able to stop it immediately. This might cause distress. You would need to consider any health and safety aspects of having a distressed patient in a pressurized environment.
I don't know about the efficacy of treatment, but I can well understand being prepared to do whatever might help.
CS