Development of a measurement procedure for the characterization of a special mattress for the treatment and prevention of pressure ulcers.

The aim of this thesis is to assess the efficiency and efficacy of a mattress for the treatment and prevention of a very common and spread complication to many diseases during hospitalization, that are Pressure Ulcers (PU). PU, also known as pressure sores, bedsores, decubitus ulcers and pressure injuries, are wounds caused by a decreased local circulation due to a high interface pressure (IP) [1]. A prolonged weight of the body or a limb, mixed often to shear forces can cause pus, and remaining seated or lying for an extended period of time increases the risk of pressure ulcers development, because the tissue remains squashed between the underlying surface and the bone prominences [2-4]. A key study [5] evidenced that also a small amount of pressure for a couple of hours in normally sitting conditions could lead to pressure ulcer development, due to the weight redistribution over a smaller area [6-7], causing oxygen depletion in the underlying muscles and tissues [8]. Annually, PU affect an estimate of 250,000 to 500,000 individuals in Canada with an overall estimated prevalence of 26.0% in healthcare institutions. In Germany, the prevalence rate is estimated to be 10 to 25% among ward patients and as high as 30% in rehabilitation centers. In one Austrian public hospital, incidence rates were between 1.39% and 7.98% for Stage 1, 0.14% and 1.52% for Stage II, and 0% and 0.88% for Stage III PU [9]. These lesions can rapidly spread from an apparently surface lesion to a larger tissue breakdown, involving skin, muscle and bone. The impact of PU involves not only economic burdens for the healthcare providers, but also the individual suffering due to the impact on the patient’s general physical health, body image, independence and level of control. The benefits of prevention are clear; it is highly preferable to reduce the incidence of pressure sores rather than managing the deleterious impacts of this disease. In particular, for geriatric and stroke patients in acute/critical care settings, the PU are indeed a threat [10]. Among the victims due to this disease, the 73% are found in the group of the over 65 years old. In 2005, a research [11] found that 28.7% of intensive care units (ICU) are prone to develop a PU. Many devices exist to slow down PU, especially in subjects with limited mobility or bedridden, and this condition coupled with a pathology that causes a weight increase is the worst condition possible for the development of this pathology. Among the different devices the most common are the Alternating Pressure Air Mattresses (APAMs), which can be of two kinds: alternating pressure air replacements (APARs) and alternating pressure air overlays (APAOs) [12]. Even if studies comparing different APAMs proved that they are more efficient compared to the standard hospital mattresses, they also evidenced that two-cell ones are more efficient in relieving the contact interface pressure (CIP) rather than the three-cell ones, and no significant differences are found among the different two-cells APAMs. The aim of this research is to study the effectiveness of a device composed by a large number of individual cells and in order to do so we will have to define a measurement procedure to assess its characteristics, with a high degree of reliability and repeatability.