A friend of mine's 5 yr old dane has this as well. His is managable, but he does need to be on a fairly mushy diet. He gets canned food mixed with water until it's an oatmeal consistency. A piece of kibble here and there doesn't appear to harm him either as he usually finishes off his sister's food, he just can't have that much or her will throw it back up.
I've babysat for him several times and he only coughed up a little bit one time. He will cough on occasion, it actually sounds like he's clearing his throat, but otherwise he lives a very normal life. B/c of his mega, he was only around 100 lbs when they adopted him, he is now a slightly chubby 160.
Depending on how severe it may be, it can be very manageable and the pup can live a very normal and active life with normal life expectancy.
