Propped Up on Pillows: The Stack Height Behind a Stated Backrest Angle, and the Mouthful It Allows

This study uses geometry and stated assumptions to examine what a stack of ordinary pillows actually provides for a patient who cannot sit up and who is fed at home without a nurse or an adjustable bed. A pillow with an uncompressed thickness of 0.12 m compresses to an effective thickness of 0.072 m under the stated load. With a torso support length of 0.60 m, stacks of 1 to 6 pillows deliver backrest angles from 6.89 degrees to 46.05 degrees after compression. Reaching a target angle of 30 degrees requires a stack height of 0.3 m and 5 pillows, which deliver 36.87 degrees, while a target of 45 degrees requires 0.424 m and 6 pillows, which deliver 46.05 degrees. Under a stated mouthful rule, a meal of 400 mL takes 80 mouthfuls and 60.0 minutes when flat, compared with 23 mouthfuls and 17.25 minutes at 45 degrees. With a stated friction coefficient of 0.30, sliding without a knee support begins above 16.7 degrees, so every stack of 3 or more pillows in this calculation places the patient in the sliding range. All results are simulated from the stated assumptions, not measured.