Final answer:
The nurse should acknowledge that the PN has positioned the client correctly.
Step-by-step explanation:
The correct action for the nurse to implement is b. Acknowledge that the PN has positioned the client safely and correctly. When preparing a client for a lumbar puncture, it is important for the client to be in a specific position to allow for proper access to the lower lumbar area of the vertebral column. The position described by the PN, with the client on their side, leg straight, and head of the bed in semi-Fowler's position, is the correct positioning for a lumbar puncture. This positioning allows for easier access to the lower lumbar area, making the procedure safer and more effective.