I just did my EFR course a few days ago. We were taught that if you have no barrier to use that you can just do chest compressions if you don't want to do breaths.
For a few dollars you can buy a tiny barrier to use for breaths that you can keep on a key chain.
...of professional medical response I have yet to see ONE lay rescuer using ANY form of barrier device while performing cpr.
...9 times outta 10, there is NO cpr in progress upon arrival.
The move to ever simpler, easier protocols can only improve this dismal reality.
DSD