Hi Everyone

A little background, I have been swimming all my life, and after competitive youth swimming, competed in masters swimming up until the mid 1990's. It was then that the symptoms of what I would call a mild asthma crept in, as well as Rheumatoid Arthritis. Even though, in my last competition, I set a couple of local records, my speed was falling off drastically.
It was very frustrating.

I continued to train, but never competed again. Mostly because I was frustrated with the way my body was not cooperating.

Still I kept training. I also added weight training to the mix, and am in very good physical shape. I can manage my arthritis pretty well, but my challenge is my breathing.

So this year I have decided to enter competitions again. I am training hard, and have added jogging to my mix. It's helped my asthma/breathing a lot.
So with that I've been able to step up my swim training again.

My strong events were/are 100/200 fly 200/400IM and 200 breast.

My 200 fly training is coming along pretty good. Worked out for 1400m fly as part of my workout no problem, within the last week.

So I am working on my IM. When I switch from my fly to the backstroke leg, I start to have extreme difficulty breathing. I have to slow down quite a bit to manage my breathing.
With that, the breaststroke leg really sucks, I spend most of that time just trying to diaphragm breath and recover from the backstroke. Once I hit the freestyle leg my breathing starts to recover. It's too late though. All this happening at a mild training speed, not a race speed.
I don't know why flipping over on my back, would cause such issues. One would think, with your face out of water, and being able to breath and exhale as you like, it would be the opposite of what I experience.

The sensation I get on backstroke is a severely restricted or reduced lung capacity, almost like someone is trying to choke me. I try extending my head back, which helps a little, but not much.

Has anyone else experienced this or had anyone else on their team?

My asthma medication, has never helped in the past with this. It makes me think that it's something else besides just asthma.
Once that choking sensation kicks in, I have to combat the anxiety and panic that sets in and try to relax.

I've tried to think about forced exhaling to make sure my lungs are empty before inhaling. That only helps a tiny bit.

Any help or suggestions are much appreciated.