High concentration O2 may have some effect on N/V, but ondansetron, phenegran, droperidol or even diphenhydramine are much better choices. If intractible N/V can be cause for an admit, don't your patient's deserve ALS?
Ha... A certain ALS project near me didn't start carrying anti-emetics until about a year ago. And to top it off, most of the Medics that work there would absolutely blow a gasket if a squad requested them for N/V...
... And people wonder why I drive 45 miles to work elsewhere