Wireless Pressure Ulcer Sensor: Validation in an Animal Model.

Pressure ulcers are increasingly prevalent in an aging population. The most commonly used method of pressure ulcer prevention is pressure off-loading achieved by physically turning bedbound patients or by using expensive, single application devices such as wheelchair cushions. Our aim is to approach the problem of pressure ulcer prevention in a new way: a wireless sensor worn by the patient at locations susceptible to pressure injury. The sensor will monitor local pressure over time and transmits the data wirelessly to a base station (in a hospital setting) or smartphone (for home care). When a condition that would be harmful to tissue is reached, an alert would enable immediate direct intervention to prevent development of a pressure ulcer. The goal of this study was to validate the sensor's use in a live animal model and to lay the foundation for building time-pressure curves to predict the probability of pressure injury. Sprague-Dawley rats underwent surgical implantation of bilateral steel discs deep to the latissimus dorsi muscles. After the animals recovered from the surgical procedure, pressure was applied to the overlying tissue using magnets of varying strengths (30-150 mm Hg) for between 1 and 8 hours. Our sensor was placed on the skin prior to magnet application to wirelessly collect data regarding pressure and time. Three days after pressure application, animals were killed, injuries were graded clinically, and biopsies were collected for histological analysis. Results reveal that all animals with magnet application for more than 2 hours had clinical evidence of ulceration. Similarly, histological findings of hemorrhage were associated with increased time of pressure application. However, at high pressures (120-150 mm Hg), there were ischemic changes within the muscular layer without corresponding skin ulceration. We have developed a wireless sensor that can be placed on any at-risk area of the body and has the potential to alert caregivers when patients are at risk of developing a pressure injury. Our sensor successfully transmitted pressure readings wirelessly in a live, mobile animal. Future studies will focus on safety and efficacy with human use and development of algorithms to predict the probability of pressure ulcer formation.

Correlation of bioimpedance changes after compressive loading of murine tissues in vivo.

OBJECTIVE: Rises in the incidence of pressure ulcers are increasingly prevalent in an aging population. Pressure ulcers are painful, are associated with increased morbidity and mortality, increase the risk for secondary infections and inpatient stay, and adds $26.8 billion annually to the healthcare costs of the USA. Evidence suggests that a change in the bioimpedance of living tissue in response to continuous local contact pressure can be a useful indicator for the onset of pressure injuries. APPROACH: Thirty-five Sprague Dawley rats were subjected to various skin pressures for differing periods of time via a surgically inserted steel disk and an externally applied magnet. Contact pressure and bioimpedance were measured and correlated with tissue loading intensity and compared to clinical ulcer grading. MAIN RESULTS: Moderate relationships between bioimpedance changes and tissue loading intensity were found. Stronger correlations were found by utilizing a combination of bioimpedance and phase angle. Thresholds were applied to the bioimpedance parameters and the usefulness of bioimpedance in classifying different ulcer stages is demonstrated. SIGNIFICANCE: These results indicate that bioimpedance may be useful as an early indicator of pressure ulcer formation and has practical significance in the development of early pressure injury detection devices.

Generation of Functional Human Adipose Tissue in Mice from Primed Progenitor Cells.

IMPACT STATEMENT: This research describes the use of human mesenchymal progenitor cells for generating functional adipose tissue in vivo in a nude mouse model. Further preclinical development of the methods and insights described in this article can lead to therapeutic use of these cells in regenerative and reconstructive medicine.