Treadmill test

Will try to keep it brief but can't promise anything

Just wondering if anyone on here has had a treadmill test at a time when they've been feeling breathless a lot? I know they won't do it if you're really bad (and I assume, or at least hope, that a brittle asthmatic with exercise as a trigger, like many of you on here, wouldn't have it). Plus not everyone has suspected heart issues.

However, while I'm nowhere near brittle or severe, I am pretty breathless most of the time and I walk very slowly and tend to start getting even more out of breath and to cough if I speed up, so am a little worried about doing this test - my heart can handle it I should think but not sure about lungs! The cardiologist I saw today (massively inconclusive appt, grrr, so frustrating) has seen me breathless at rest and obviously thinks I can handle it, but does anyone have any experience of doing this test when not at their best breathing-wise? I know they have people standing by in case something happens and will stop if it gets too bad.

Of course, the way things go with me I will probably miraculously have almost normal breathing while doing it then start wheezing madly after I leave lol

Thanks in advance for any replies.