Two more things to help:
1. NAC
2. Keto
On the Keto diet, a strange benefit is a reduction of CO2 needing to be exhaled. I seem to recall up to 10% less. That greatly helps COPD suffers.
Found it. It appears to be over 20% - 30% less CO2 to expel from fat and protein instead of carbs:
Effect of supplementing a high-fat, low-carbohydrate enteral formula in COPD patients (Low Carb Helps!)
https://freerepublic.com/focus/f-chat/3803247/posts
Also, Vitamin C helps:
Dietary vitamin C intake protects against COPD: the Korea National Health and Nutrition Examination Survey in 2012 (also restores function)
https://freerepublic.com/focus/f-chat/3803267/posts
Finally, it looks like superoxide dimutase (SOD) and bicarbonate can help:
https://freerepublic.com/focus/f-chat/3803125/posts
I haver had good experience with keto also.