Deteriorating is one of the words hospitals tell us oversea nurses often make mistakes with.
That is, they understand the word but not the critical meaning it has. Hospital staff tell us that overseas nurses are likely to respond with ‘Oh dear’ on hearing the sentence above.
What the hospital staff want the nurses to do is act. The phrase is used a bit like a warning alarm. On hearing it, those treating the patient should prepare for emergency measures to counteract the deterioration.
A better response on hearing the phrase would be ‘What can I do?’