Weird. That's not the Mammalian reflex: this blocks inhalation, instead you had problems exhaling.
I agree that this looks similar to a panic attack, which often brings to hypercapnia, as the panic impedes to expell properly CO2.
There is often a vicious circle: the sensation of being unable to breath triggers more panic.
When I followed my first diving course (in 1975), using mostly the ARO (closed circuit pure oxygen rebreather, pendular type) this was a very common scenario. It did take months to be trained to control the panic sensation caused by a clogged filter, which really impedes to breath, and which does not capture CO2 properly.
Using the ARO teaches the student to gain a complete control of his breathing, which is inherently coupled with a deep emotional self-control.
But being trained in this way takes several months (6, during my first diving course).
This kind of training nowadays is not readily available even in diving schools, not certainly in commercially-oriented shops.
So actually I have no simple suggestion on how to gain proper self-control, which is the only way to be sure you will not get this problem anymore.
Of course you could try to avoid the situations which trigger panic.
But this for me is not a fully satisfactory solution: bad things happens, outside of your control. You should be sure that, even in the worst situation, you will never fall to panic and loose control of your breathing.
My experience as a young, insecure student was that getting complete self control is possible, with several months of proper psycho-physical training.
I hope that someone here can contribute information on where such kind of training is available nowadays (outside of military special forces).
