A nurse is cаring fоr а client with chrоnic оbstructive pulmonаry disease (COPD) who is receiving oxygen at 2 L/min via nasal cannula. The client's oxygen saturation has improved from 88% to 91%. However, the nurse observes that the client has become increasingly drowsy and is difficult to arouse. The respiratory rate has decreased from 20 breaths/min to 10 breaths/min. Which action should the nurse take first?