What action should the nurse take to prevent the formation of a sacral ulcer in an immobile client?

The most effective action to prevent the formation of a sacral ulcer in an immobile client is positioning the client prone with a small pillow below the diaphragm. This position helps to relieve pressure on the sacral area, which is particularly vulnerable to breakdown due to prolonged immobility. By placing a pillow below the diaphragm, the weight is distributed more evenly, and the sacral region is lifted, reducing direct pressure on the tissue.

This positioning strategy is essential because sacral ulcers, also known as pressure ulcers or bedsores, develop when soft tissue is compressed between a bony prominence and a surface for extended periods. By utilizing the prone position, the nurse can ensure that adequate blood flow is maintained to the skin and underlying tissues, thereby decreasing the risk of ulcer formation.

In contrast, while other options may have some benefits for overall comfort or mobility, they do not specifically address the critical need to relieve pressure from the sacral area as effectively as the prone position does.