Final answer:
The nurse should prioritize educating the client on the use of incentive spirometry to prevent postoperative pneumonia and atelectasis.
Step-by-step explanation:
The intervention that the nurse should prioritize in an effort to prevent postoperative pneumonia and atelectasis in a client with reduced mobility following foot surgery is educating the client on the use of incentive spirometry. Incentive spirometry is a breathing technique that helps to expand the lungs and improve lung function. By using an incentive spirometer regularly, the client can prevent the build-up of fluid or mucus in the lungs, reduce the risk of pneumonia, and prevent atelectasis.