Caapi is a vasodialator.
I had one particularly challenging experience where I thought I couldn't breathe; the intensity of the awareness in my lungs was so much that it was just totally overwhelming. I called for my sitter, and I was stuck somewhere close to hell (not entirely, but maybe on the outskirts) for a few hours.
When it was all said and done, I was like, "OMGWTF JUST HAPPENED!?!?!?!" I grilled her about what was happening with my body, and she said it sounded like I was on the couch, sleeping.
It was more the PERCEPTION of breath that was altered, rather than breath itself.
Now, when these things happen, I just focus on staying calm, breathing deeply through my stomach (it's particularly intense if you are being physically invaded/penetrated by spirits when the admixture hits), and it DOES PASS.
If you fear and panic, it gets A LOT WORSE.
The answer for concerns about anything... including breath... is breath!
Some things will come easy, some will be a test