An air sac for use on a low air loss bed. The air sac is provided with a releasable connector for retaining the air sac to the low air loss bed and with a nipple for receiving air from a gas supply source to inflate the air sac. The air sac is also provided with a cutout which allows the patient to be rolled toward one end of the air sac when the air sac is inflated, A pillar is provided on the end of the air sac toward which the patient is rolled when the air sac is inflated to retain the patient on the air sac. The air sacs are arranged in sets with every other sac mounted to the frame of the low air loss bed in alternating arrangement whereby the patient is rolled first in one direction when the air sacs of one set are inflated and then back in the other direction when the air sacs in the first set are deflated and the air sacs in the second set are inflated.