The inflatable air mattress is placed on top of a conventional mattress, and is retained in place by straps that are secured to the bed frame. In the preferred embodiment, the inflatable air mattress includes a pair of identical chambers, the chambers being of rectangular shape and separated by a hinge line. Each chamber is divided into several, parallel cells, and a separate air pump is connected to each chamber. When energized, the pump forces pressurized air into the chamber and rapidly fills same. As the chamber is filled, it expands and is capable of rotating a patient positioned thereon, through a 90° arc of motion. With the intervention of a health care worker, or a nurse, the patient may then be rolled over from his front to his back, or vice versa.