my insurance charges a $150 copay for ER visits that do not result in an inpatient admission. what is an inpatient admission? if someone was in the ER for a few hours and gets an IV but is not in their own room, etc. is that considered inpatient admission or not?
i was on a hospital bed in a hallway for about four hours.

If you were just went to an emergency room and were there for a few hours, that is considered outpatient. Inpatient would be if you stayed more than a day which is much more costly (and that does not mean just a few hours overlapping midnight).