Was your doctor satisfied with the results/readings they were able to obtain? If yes, you were successful, if not your doctor may want to consider a "chemical" stress test. I don't know anything specific about what I call the "chemical" (medically induced may be a better terminology) method other than the patient doesn't get on a tread mill, their heart is put into a stress/load condition by injections (I believe). I bring this up only as further evidence that your physical test may have satisfied the need that was intended.
As for COPD, I have only a simple sinus congestion problem, and that can cause me breathing difficulty -- of course I can breath through my mouth, but that leaves me feeling like I am suffocating. I assume COPD is even more difficult to deal with.. My empathy on that point is sent.
I doubt whether anybody "finishes" stress tests. They're designed so the person under test eventually reaches failure. I believe the "stress test" is standardized, so no matter where you go, the test is the same. If that is the case, ten minutes really isn't that bad if you are 49 abd have COPD. At 62, I was only able to do 13 minutes, and I'm in pretty good shape for my age. So don't feel like you "failed". The test is made that way.