The ego-T is what I quit with. They are cheap and can work, but as already mentioned there is much better equipment available today. I might suggest the Aspire Zelos with the Nautilus 2 tank in a kit. A little pricier than your ego but a much better
vaping experience all the way around.
There are many variables involved in
vaping. I quit upon my doctors recommendation and coughed a lot of stuff out of my lungs for a couple weeks.. was horrible but in the end I could breathe so much better.
I never had "lung pain" though. It might be a bit of sensitivity to pg, however, or it might be related to your COPD. that said, there are MANY COPD sufferers who vape successfully and show great improvement in their condition.
If I were you on top of speaking to your doctor, I would try a more modern set up such as the Aspire Zelos with the Nautilus 2 tank. You might find yourself more successful with that, as well as have less problems with the transition from smoking to vaping as with that kit you can try a little bit higher vg level.