B, remember that hyperbaric treatments are nothing more than sitting in a pressurized, oxygen rich environment. It is fundamentally different than radiation or chemo; both of those are designed to KILL cells, and do that very well...both cancerous ones and healthy ones. It's the cellular damage that makes you so sick.

Hyperbaric treatments actually encourage cellular growth by temporarily increasing the density and quantity of blood vessels in the affected areas. If he's having a lot of negative symptoms, chances are very strong that he's got something else going on; if anything, the increased oxygen levels in his body should make him feel more alert and generally a bit better overall, not sicker.
Wayne