I used a BiPap before transplant. I found that the one in the hospital was so much easier to adjust to than the one at home. The one at home forced air into my stomach and caused me to belch throughout the night, lol. Funny now, annoying then... The best thing I can say is to wear it for as long as you can at one time. I found it easiest to use at night since I can sleep through just about anything. I could wear it about 4-6 hours before the straps would hurt (since you have to wear it so tight) but found that rotating different nose pieces helped with it not hurting as much. I used the nasal pillows and the nasal mask. They never gave me the full mask, just told me that most people didn't like them. I don't know if that's true or not, but oh well...
Post transplant I haven't had to use any oxygen systems and it's been fabulous <img src="i/expressions/face-icon-small-happy.gif" border="0"> Best of luck with everything!!