Hello, I am a neonatal nurse in England and the primary responsibility would be the nurse caring for the patient. However, all who come into contact with the patient has a responsibility to give optimal and high quality care. Hence, if the nurse is not present at the time the respiratory nurse observes desaturations, it is the responsibility of the respiratory nurse to inform the appropriate personnel. During care on our unit, obviously nurses have to have a break. Therefore, another nurse remains in the room and it is the responsibility of that nurse to observe the patient for the nurse who has gone on their break. Hope this information helps. Do you follow guidelines in the US. We have the NMC code of conduct.