The authors describe a novel system for sensing and displaying the distribution of contact pressure caused by a patient's lying on a hospital bed. The system includes a flexible, pressure sensitive mat, electronics to activate the mat, a small computer to process data, and a color video display. The present prototypes can sense pressure at 1,536 discrete locations in a rectangular grid of 24 x 64 nodes, each node representing an area of 4 cm2. The computer receives data from each node and displays the results as a false-color map, refreshable every 5 seconds. The pressure sensitive mat itself includes two orthogonal arrays of ribbon-like conductors, composed of silver coated nylon fabric, which are separated by insulating open cell foam rubber. The system monitors the electrical capacitance between selected pairs of horizontal and vertical conductors on opposite sides of the foam. The crossing points form pressure sensitive nodes. Increased contact pressure compresses the foam, thereby decreasing the distance between the conductors and increasing the capacitance. Node capacitance is determined by measuring the current through it from a voltage source. The outputs of the various nodes are scanned, normalized, and converted to pressures using the known compressive stressstrain relationship for the foam, and the data are then displayed as a false-color image of the pressure distribution.
Date of this Version
Babbs, Charles F.; Bourland, Joe D.; Graber, George P.; Jones, James T.; and Schoenlein, William E., "A Pressure sensitive Mat for Measuring Contact pressure Distributions of Patients Lying on Hospital Beds" (1990). Weldon School of Biomedical Engineering Faculty Publications. Paper 72.