A guard works alone with individual responsibility, a nurse does longer in training but at that stage would rarely have sole responsibility.
I was in hospital recently. It was a 4 bay area. bloke opposite me started to get ill during the evening. went a horrid colour. A nurse was tending to him at 3am and he went into a fit (which people do when their body functions become degraded). She hit the panic button and got the crash team there in seconds flat. She made no fuss about it. Probably saved the blokes life as his airway was constricted.
I'm sorry, but guards dont do that on a regular basis. Soon after she was still on the ward looking after the other patients. The one next to me had only come back from prostate surgery at 1900 the evening before so was still on 15 minute obs, and needed his catheter bottle contents logging and emptying.