I had severe asthma as a kid and it's something that rarely if ever caused me to miss practice much less a game. A big part of asthma is just not being able to take a deep breath.
It would sometimes take me time to be able to inhale enough to get enough oxygen to function. It was like a wall that I had to push through. Once I pushed through that wall I was fine, but i'd be in pregame warmups struggling for breath. I had to push really hard at times to get what I called my 2nd wind...
My lungs just would not accept enough air in to allow me to stress my body. It's something that I dealt with all my life. I coud see how factors could come together that made it impact you but not often and with the management stuff they have now it would have rarely been a bother.