Pursed Lip Breathing does work and it does help. It puts your mouth in a position that forces a longer exhale, and that's what helps. It's wierd, but with COPD, it's not that you can't get air in, it's that you can't get enough of the stale air out. So the exhale is way more important than the inhale. You want to do it correctly: inhale and then exhale through your mouth, pursing your lips as if you were going to play the flute. Don't push the air out really hard, just make sure that your exhales are at least twice as long as you inhales. That will keep you from getting sob as quickly and will help you continue on even if you are sob.

I do it, not sure it helps but it can't hurt