I'm sorry to hear about your friend's COPD. I doubt that he will ever improve until he stops smoking. It took the fear that I was near death to scare me into quitting, after smoking over 40 years, but when you let it go that long, the damage is hard to repair. I only have about 25% of the normal lung capacity of one who has never smoked, according to a spirectomy (spell?) test I had the other day.
My sister was diagnosed with COPD a few months ago, and she didn't like having to drag oxygen tanks everywhere she went. But she is one of the lucky ones who quit smoking in time, a year ago, and her lungs recovered. She can walk and still maintain 91% oxygen on room air where as I go below 80% walking with 4 liters and have to increase it 6 liters on exertion...that's as high as home systems go...then what? I don't want to spread doom and gloom, but show this to your friend and maybe he'll see that he has to stop smoking. Nobody loves cigarettes more than me...nobody...but I refuse to let them kill me, at least not without a fight! By "them" I mean the tobacco companies that supposedly enhance the tobacco with addicting chemicals and the government that subsidises a known cancer causing product and reaps in big bucks on taxes from them! I keep looking for new treatments.
I don't think the tremors are from COPD. Is he diabetic, or has he had his thyroid checked? I got pretty shakey before I found a doctor who believed in adding T3 to the T4 thyroid hormone. Does he feel really cold too? If you Google search "cause of hand tremors" a lot of possibilities come up.
I hope I've made sense. I'm really sleepy today.