I agree with what everyone else has already mentioned. Being on O2 - if you need it - can help EVERY organ in your body. Even if you feel "okay" without the O2 if your sats are low then the rest of your body is affected - be it kidneys, heart, muscles, brain function whatever it is affected.
For me when I started using O2 - I had a major increase in appetite. I gained about 6-7 pounds. I started sleeping better. I had lessened anxiety. I was not so short of breathe - though I will say I still got short of breath and tired it was not as bad as without O2. I did NOT feel as weak and fatigued while using O2 either. Also to say I noticed that alot of my aches and pains pre transplant would dissipate when I was using O2.
I don't know about it improving lung function so much in regards to the actual numbers but I will say it will at least make you feel like you are breathing easier. At least it did for me. When I was using O2 I finally felt like I was breathing at points. Before O2 I felt like I was just sucking in air for no real reason - I never felt like I got enough. My "thirst" for air was quenched when I started on O2.
Hope that makes sense.
Love Linds