I also found an article about breathing and panic attacks:

"When you try to calm your anxiety and panic
with deep breathing you actually reduce the carbon
dioxide levels in your blood by 50% in as little as 30
SECONDS.
In schools we were taught that carbon dioxide is
harmful to our bodies, but actually it is CRUCIAL to
maintain a proper acid-base or pH levels in the
blood.
“Overbreathing” raises the pH level in your
nerve cells and they become more excitable and
sensitive. And as a result of that, in less than a
minute, you start experiencing different physical
symptoms: Heart palpitations, chest pain, dizziness
and faintness, just to name a few.
So beating anxiety and panic with deep
breathing is just a bad idea. One that will never
work."