Final answer:
The nurse's first action should be to disconnect the mechanical ventilator and manually ventilate the patient to ensure they are adequately ventilated and to determine the cause of the high-pressure alarm.
Step-by-step explanation:
A nurse is caring for a client with emphysema who is on mechanical ventilation and showing signs of anxiety and restlessness with the high-pressure alarm sounding. The first action the nurse should take is to disconnect the machine and manually ventilate the patient. This immediate response is necessary to ensure the patient is getting adequate ventilation and to assess the cause of the alarm, which could be due to increased airway resistance or a problem with the ventilation machine itself. Once manual ventilation ensures patient safety, the nurse can proceed with obtaining arterial blood gases (ABGs) to check the patient's oxygenation and carbon dioxide levels, providing sedation with medications like propofol if necessary, and instructing the patient on synchronizing breathing with the ventilator.