Interesting if true. She should at least consider getting a thorough medical work up concentrating on lung function. If it is a function of the PO2 then she should have the same symptoms when she dives near max sport diving depths or a little beyond. (simulating same PO2 a nitrox dive would give at shallower nitrox depth)
Good luck to your lady friend. Get her to see a pulmonary specialist.
I'm not in the habit of writing nonsense; I'm well known enough in French diving circles to avoid doing so.
The lady has been seeing a pulmonologist every year since we advised her to consult a doctor.
She is trained to dive to a maximum depth of 20m. She has always used a Nx30 maxi, which makes her cough.
Her pulmonologist has authorized her to dive since he has been treating her, limiting the use of nitrox, which is still allowed, but diving more often with air.
In France, every diver must provide a medical certificate signed by a doctor who is responsible in case of a problem.
So I assume that if he authorizes it, it's because he knows what he's doing.
Once again, to respond to the “god of diving,” I am not a doctor. And even less so a lung specialist.
Since she doesn't like diving while breathing air, she has reduced the number of her dives so that she can continue diving with nitrox.
When she dives several times over a weekend, she alternates between nitrox and air diving.
To date, the doctor has never said that he disagrees with her choice.