If your bronchitis gets so bad where it affects your oxygen intake, that is a sign to get to the hospital and get treatment. And yes, it can lead into pneumonia. Just recently was in hospital for pneumonia and the day I went in my oxygen normally in the 90's went down into the 70's and gasping for air even going to the car.

I usually get them together and wind up in the hospital with pnuemonia. Not fun.

I've got to have mine done the pneumonia and 😷 flu 😷 shots asap before the real winter 🎿 sets in so I'm protected against it has much as possible.
I get out of breath just walking to the local shop around the corner its approx 1000 yards there and thousand approx back in in the process of having my asthma meds changed so it makes it easier to breath