o2

I have been working LTC/ subacute for about 6 months now and I am confused about some of the standards. I assumed in order to straight cath a patient, one would need an order from the doctor each and everytime. Or it would be documented it would be ok to do it. But, some of the nurses say: oh that doctor wouldn't care. and another question,
is changing a nasal cannula to a non-rebreather considered a nursing judgement? What exactly is a nurse allowed to do to help a patient before a physician is notified? I work 11-7 and I find many of my problems arise before I get there. Thanks for any input or guidance.