Most hospitals have replaced, or are in the process of replacing, standard mattresses with static pressure-reducing mattresses, usually made of high-density foam. But not all mattresses are created equal. Hospitals spend thousands of dollars each year to purchase foam-replacement mattresses, and too often these decision are made by cost comparison. Instead, decisions should be based on knowledge of the characteristics of foam in the context of effective pressure reduction. Such characteristics include base height, density, indentation load deflection (ILD), and contours, defined as follows:
- Base height measures foam from its base to where the convolution begins-not the peak of the convolution. The base height should generally be 4 inches.
- Density, the weight per cubic foot, measures the amount of foam in the product and reflects its ability to support the patient's weight. Recommended density is 1.3-1.6 pounds per cubic foot.
- ILD measures the firmness of foam and is determined by the number of pounds needed to indent it to a depth of 25% of the thickness with a circular plate (e.g., in the case of a 4-inch foam mattress, ILD would measure the number of pounds needed to make a 1-inch indentation). ILD indicates the ability of the foam to distribute the mechanical load. The goal is to have a low ILD (an ILD of approximately 30 pounds in recommended).
- ILD ratio, recommended to be 2.5 or greater, reflects the relationship between conformability and support. A relationship of 60% ILD: 25% ILD is needed (e.g., if 30 pounds makes a 1-inch depression, then at least 75 pounds would be needed to make a 2.4-inch depression in the same foam).
- Contour is the surface of the foam, which may be in either slashed, smoothed, or egg-crate design.
—Karen S. Clay, RN, BSN, CWCN