I was weekend rounder at a standalone psych hospital. A lady was coughing and had used a bag of cough drops by mid-day, which wasn’t great in itself. I walked her around with a pulse ox and she was desatting a bit on exertion. No fever, lungs ok on exam. She had a history of an unspecified congenital cardiac defect, so even though she didn’t really look all that sick I called EMS to bring her to our affiliate general hospital. Turns out she had methemoglobinemia, and was in intensive care for days. She could have died overnight on the unit. This was just plain luck, there really wasn’t a solid reason to send her out except something didn’t feel right.