I really should put this into a post of it's own... But to cut a long story short - You can get lots of symptoms from hyperventilating, including chest pain, pins and needles, dissyness, vomiting, painful throat, painful breathing, cramps and towards the end fitting and unconsciousness. It's not massively dangerous, and is normally self limiting. The only treatment is to calm the patient down (unfortunately we aren't allowed to slap hysterical people like they do in the old movies - no matter how much we'd like to) I spent an hour on scene because I cancelled the ambulance (I'd rather waste my time rather than an ambulance that can actually take sick people to hospital). Some people can take an hour to calm down, others take five minutes and the patient didn't want to go to hospital. And yes, when the ambulance turns up I can often hand over responsibility to the crew (but I do hang around if the crew need a hand dealing with the patient).