In 1988, American Health Systems introduced the first pressure reduction mattress using a surface design called Interface Surface Technology, or IST. IST not only addresses pressure reduction and patient comfort, but shear reduction as well. Over 500 individual polymer cells conform to the shape of the patient, and self adjust as the patient changes positions. Because the cells are independent of each other, they can move "with" the patient as the patient moves on the support surface, and this reduces shearing forces.