Not strictly 'pressure breathing' which is quite another event, but yes, there is an over-pressure provided at altitude to improve the oxy content.
For the other 99% of occasions surely a few seconds spent correctly establishing the crew on O2 and prolonging their time of useful consciousness would be time well spent?
- did I not say that?
We were discussing
and suffer a sudden depressurisation, useful consciousness circa 10 secs,