[Andrew]

I would like to offer some suggestions about airline oxygen. There are organisations that promote the free use of oxygen for travellers who need it e.g. EFA.
There are organisations and websites which list the Airlines that are Oxygen 'Friendly'.

The FAA has a list of Portable Oxygen Concentrators that are allowed by them. They are not always suitable because of Batteries and /or suitable power sockets. Also generally passengers cannot carry on their own oxygen bottles , but if the airline supplies it or authorizes a 'rental' company it is available , at a cost.
I work for a company that supplies the oxygen equipment for therapeutic and First Aid use and I am aware of the mixed responses that have come from airlines when you discuss the use by passengers.

We very much welcome this debate as the industry has not taken enough action.