A nurse is caring for a client who is on bed rest. Which of the following interventions should the nurse implement to maintain the patency of the client's airway?

The correct answer is D: Promote incentive spirometer use. This intervention helps prevent atelectasis, a common complication of prolonged bed rest. Using the incentive spirometer helps the client take deep breaths and improve lung function, thereby maintaining airway patency. Encouraging isometric exercises (choice A) does not specifically target airway patency. Suctioning every 8 hours (choice B) is not necessary unless there is a specific indication. Giving low-dose heparin (choice C) is used to prevent blood clots, not to maintain airway patency.