Pressure ulcers are a major health problem in the United States, affecting 1.3 million to 3 million individuals. Among hospitalized patients, the prevalence of pressure ulcers is 10% - 17% and the incidence is 2.7% to 30%, particularly if the patients are elderly (70%), critically ill, or have previously sustained a spinal cord injury (38%) Further, 12% to 66% of patients undergoing surgery develop a new pressure ulcer – a complication that is twice as likely to occur if the operation lasts longer than four hours. Overall, the individual, institutional, and societal consequences of new pressure ulcers are clear – they may double the risk of mortality, lengthen the hospital stay by a factor of five, and increase the cost of care ten-fold for a Stage IV ulcer as compared to a Stage II ulcer. These data drive the question: What are the critical factors in the early detection of tissue injury and, thus, in the prevention of pressure ulcers?

A 10-subject pilot study, with repeated measures design, will be conducted to identify preclinical markers of impending heel pressure ulcer formation among adult patients who undergo elective hip replacement surgery. There are four aims of the study: 1) describe the baseline and serial morphological characteristics of the skin and subcutaneous tissues overlying the pressure-loaded surfaces and comparator sites on the heels using a Multi Spectral Polarized Light Imaging System (MSLI), 2)  determine the baseline and serial plasma levels of the proinflammatory cytokines, which are associated with skin injury, 3) measure baseline and serial quantities of transcutaneously-expressed chemicals collected from areas of pressure-loading, using enzymatic assays or mass spectroscopy, and 4) establish the relationship between changes in the morphological characteristics of the tissues overlying bony prominences and age, nutritional status, local blood oxygenation / deoxygenation, skin inflammatory cytokines, and the transcutaneously expressed chemicals which indicate local tissue ischemia or injury.

Data will be submitted to Statistical Package for the Social Sciences (SPSS) Version 15.0. Descriptive statistics will be computed on the demographic and nutritional data, in order to describe the sample.
For the first research aim, the MSPLI images will be analyzed qualitatively to describe tissue characteristics at baseline and to detect and describe changes in the pressure-loaded tissues of the heels, as compared to baseline and the ipsilateral medial heel, at each successive data collection point.

Since the sample size is small, the non-parametric Friedman matched samples test will be computed to determine whether there are significant differences in the levels of oxygenation and deoxygenation, skin cytokines, and levels of transcutaneously expressed chemicals over five time periods. If the Friedman test results in a significant finding, a Mann-Whitney U with Bonferroni correction will be used for post-hoc comparisons. Guided by the post-hoc comparisons, the MSPLI images will be re-examined to quantify tissue changes which correspond with elevations of other biological markers of tissue ischemia / injury.
Data from this 10-patient pilot study will support and guide subsequent applications for funding to further study of methods for early detection and interventions to prevent pressure ulcer formation.

Principal Investigator: Virginia Capasso, PhD, APN-BC

Funding: Supported by Association for the Advancement of Wound Care ($5000).