Commercial donut pillows are used during lengthy surgical operations. With the patient anesthetized, the multiple pressure points on the head and wrinkling of the skin cut off blood circulation in the face, which leads to facial decubitus ulcers [1].
Foam materials, which are used in these pillows, are very effective in reducing pressure points by transferring pressure into shear stress. However, this same shear stress leads to wrinkling of the skin which generates sores.
From the point of view of the pillow mechanics, pressure normal to the pillow surface is related to normal stress in the pillow. Reduction of this normal stress implies a reduction in pressure points and an increase in shear stress. However, an increase in the shear stress leads to increased wrinkling of the skin. Thus, the optimal pillow design, which reduces sores due to pressure points and wrinkling, would be characterized by the design...
