Hi again, Mike and welcome!! We're glad to see you are engaging within the community, already!
While I am hopeful others in the community will see your inquiry and respond by sharing their own experiences managing this disease, I have something to say too.
For some folks with a COPD diagnosis, being 'inverted' in the position you described (downward facing dog), can pose challenges. With one's torso angled downward, the diaphragm and lungs (in the chest cavity), are also inverted. The organs in the abdominal cavity will also be pressing against the diaphragm making it more difficult for it to descend during an inhalation.
It may be harder to breathe in that position for some patients. Do you think this is what is happening in your case?
Wishing you well,
Leon (site moderator COPD.net)