Depending on the problem causing the symptoms, perhaps massage along these lines could help: http://youtu.be/EwA3wU-XuY0
Although this video seems to be made specifically for those with Cystic Fibrosis, I have known this kind of work to loosen phlegm for others, too.
In the absence of a therapist, a very much reduced version of this effect can be achieved by tipping one's chest upside down and shaking about, breathing deeply, huffing breath out, deliberately coughing, and/or hitting one's chest and back with a rolled-up towel or a cushion.
Three positions can be useful:
a) stand behind the sofa with the thighs pressed up agains the back-rest, then lean forward, bending at the hips to hang one's head down towards, or on, the seat of the sofa;
b) lie face-down on the bed, and then inch forward, until not just the head but the whole upper body is hanging down over the end of the bed;
c) lie curled up on one's side on the bed, and build a "mountain" of cushions in front of the belly. Then roll over up onto the cushions, so as to lie with the hips raised and the head and lungs "semi-hanging" down.
Disclaimer: please, for such exercises, take all the sensible precautions, like wearing shoes with a good grip, no loose carpets around, be sure to first place a sturdy dining-room chair nearby, to grab to help get oneself back upright again safely. Probably best to have someone else standing nearby when trying these movements for the first time.