There is not a mattress in the world that will prevent heel pressure ulcers in arterial or diabetic limbs. If the blood cannot reach the tissue, then the tissue will die. Any slight pressure will cause a pressure injury.
Pressure ulcers are 80% more likely to occur in heels when sitting in a chair due to the hardness of the floor or the stool if the legs are elevated and heels are placed on the stool.
Heels are difficult to elevate when sitting out if the person is mobile. If a heel elevator is used and the person stands to walk, it could be a trip hazard. This is not the same issue in an immobile patient.
To ensure heels are protected when in a chair, there are heel gel pads (Kerrapro and Aderma) which are on prescription. These pads can be placed under a sock or a double blue line and will protect the heels when in bed or when seated in the chair.
In bed, in those with arterial disease or diabetes, heel elevators would certainly be required. This can be two pillows placed lengthways under the legs with the heels hanging over the end of the pillow. If this is used, then a third pillow should be placed across the feet in order to support the feet in order to prevent foot drop. Nevertheless, the heels should be suspended.