The subject will be placed in each of the standard positions for the experiment: supine decubitus (SD) right lateral decubitus (RLD), left lateral decubitus (LLD). SD measurements will be made at 0, 30 and 45 degrees of inclination to bed. RLD and LLD positions will be evaluated with a body inclination of 30 and 90 degrees, aided by pillows, as is done in routine clinical practice. The subjects will lie down on a memory foam mattress for an articulated bed, as are commonly used at home, residential or hospital care. Between the subject and the mattress will be inserted the pressure measuring surface. Measurements in each position will be made during intervals of 0-4 hours in the same position (SD-RLD-LLD) in each of the inclinations of the bed (0º, 30°, 45 °) or body (30º, 90º), respectively.