Have you ever had to administer mouth to mouth resuscitation

Yes.

https://revision3.com/philipdefranco/kate-vs-elmo

The man was in diabetic shock and had just been fed applesauce before he completely collapsed.

During the CPR he vomited in my mouth.

I spat it out, cleared his mouth, established his airway, and continued CPR.

After the ambulance came (this was a small hospital without an ER) I walked myself into the nurses station, grabbed an unopened bottle of hydrogen peroxide despite the nurses at the station saying I was unauthorized, rinsed well, brushed my teeth with a hospital toothbrush and toothpaste (sealed of course), then read the on duty head nurse the riot act in triplicate for not having the damned AMBU BAG where I could find it!

Then I went back to work.

The next day I reported the unit for not having said damned ambu bag readily available.