These chambers are able to accelerate healing and even instigate restoration processes. The bubbles themselves essentially rebuild the body but can only work with what's already present. They can't make something out of nothing. At least chambers of this age can't. There are limits to what this machine can do and a lot of the healing will need to be done outside of it.
There are chambers capable of complete restoration but they're not very common and they can sometimes be extremely temperamental. They're only really used for the most severe cases and there are waiting lists for every one of them that's available.
Izzy's very lucky to be in this one here. She'd be dead without it.