Final answer:
The correct instruction for a client with a chest tube who is ready to ambulate is to ensure that the drainage system remains below the level of the chest to prevent backflow and maintain effective drainage.
Step-by-step explanation:
For a client with a chest tube that is attached to a closed-chest drainage system and needing to ambulate, it is critical that the nurse provides the proper instructions to maintain safety and the integrity of the drainage system. The correct instruction from the options provided is B) Ensure that the drainage system is below the level of the chest. Keeping the drainage system below chest level utilizes gravity to aid in proper drainage and prevents the backflow of fluids into the pleural space, which can lead to complications. Option A, clamping the chest tube, could lead to a tension pneumothorax if not managed properly, and should not be done without a provider's order. Option C is incorrect as it risks the backflow of fluids, and Option D, disconnecting the chest tube, is dangerous and could lead to serious complications including infection and pneumothorax.