The purpose of hyperbaric chamber is to supply more oxygen to the brain cells, so that the cell death slows how and the toxins are destroyed. Hyperbaric oxygen is an established treatment modality for Alzheimer's disease, for which, drugs are still the better option.
It will slow down the progression of symptoms of AD, but will not reverse the process. It can not recover the functions lost by the neuronal cell death.
Of course, doing both, medicine and hyperbaric would still be a great option. Look for hyperbaric centers that are "out of network" providers and the cost can be much less $150-$250 per dive instead of $2000. One in Birmingham, Alabama is affilliated with the Fritz Wellnes Institute at www.****.***