Hi Kazal,
I would expect that your OH will do a similar test as to the ones I did, which is to see how strong/weak your lungs/breathing is.
Mine was in 3 parts, you insert the mouthpiece & nose clip and are given instructions to breath in and out, one is soft, the other is hard, and the last one they cut the breathing pipe off in between breathing.
It didn't work for me at first, which she says never does, but after a couple more time I succeeded.
Is your OH doing any exercises at home, I don't mean heavy ones, but deep breathing as much as he can. I find the flutterer (on prescription) helps a lot.
I have been looking at 2 apparatus I found on line, one is a salt pipe, and the other a breathing device, but going to ask my Doc before I spend the money.
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I will give anything a try to feel more comfortable on a daily basis, and sure you & your OH feels the same, so good luck and try and let me know how you get on.