Final answer:
The nurse should first assess the client's respiratory status to determine the cause of the high-pressure alarm and the client's anxiety and restlessness.
Step-by-step explanation:
The nurse should take the action of assessing the client's respiratory status first when a client with emphysema who is receiving mechanical ventilation appears anxious and restless and the high-pressure alarm is sounding. This is because the high-pressure alarm indicates that there may be a problem with the client's respiratory function or the mechanical ventilator. By assessing the client's respiratory status, the nurse can determine if there is a need for intervention such as suctioning the endotracheal tube, administering a bronchodilator, or notifying the respiratory therapist.