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Instrument for Pressure Ulcer Detection (I-PUD) University of Pennsylvania Department of Electrical and Systems Engineering AUTHORS GROUP 21 Ashish Chauhan EE’05 Kashif Merchant CTE ’05 Jialing Wang CTE ’05 ADVISOR INTRODUCTION HARDWARE A pressure ulcer is an area of unrelieved pressure over a defined area on the human body, usually of bony prominence, resulting from restricted blood flow, which can even lead to cell death in that region. Pressure ulcers are a significant clinical problem especially in patients with acute and chronic immobilizing conditions. The only prevention method is changing their positions in the bed every two to three hours, which requires high level of nursing and medical management. The Manual Blanching Test for early stage diagnosis is the sole method used in the clinical environment. Due to the masking caused by high melanin levels, this method is inadequate for ulcer detection on dark skinned individuals. The I-PUD will overcome these limitations while providing the researchers with visual graphs and quantitative data, which can be documented and used for future review. The I-PUD comprises of three sensors: photo, temperature and pressure. The photo-sensor circuit has two elements: the photo-emitter and the photo-detector. The light is emitted from clear green LED’s (wavelength 564nm) which are pulsed at 1 Hertz using the 555 Timer. The photodiodes, shielded from ambient light, are optimized for receiving light of wavelength 540-580nm, and collect light reflected from the skin. The temperature sensor consists of a thermistor in an inverting amplifier configuration, using the LF347 wide bandwidth JFET op-amp. The pressure sensor is a noncompensated force sensor that uses a bridge configuration to output a given voltage. The output of this force sensor is also amplified. The voltages from the three sensor circuits are sent to the DAQ card. Detection of the ulcer is based on two principles: light reflectance and temperature measurement. Hemoglobin and skin pigments are the main color producing compounds in the skin. Oxy-hemoglobin absorbance displays characteristic maxima at 542 and 577 nm. Thus by using LEDs and photodiodes which operate at peak wavelengths of 564nm, the I-PUD can detect pressure ulcers due to differences in the reflection of light corresponding to varying amounts of blood components under the skin. As ulcerated areas can have an increase in surface temperature of up to 5°C from normal body temperature, the confirmatory test is conducted by measuring this temperature difference over the diagnosed region, using a thermistor. A pressure sensor is incorporated into the I-PUD to prevent the user from pushing the device too hard against the skin and disrupting the blood flow and thus the data readings. SOFTWARE Dr. Jorge Santiago DEMO TIMES Thursday, April 21, 2005 Times:_____________________ ABSTRACT With the high level of advancement and sophisticated technologies in the medical world, some very common conditions and diseases have remain neglected even today. The I-PUD is a low cost, reliable device that should relieve the economic burden of pressure ulcer care in the US, estimated to be $3-6 billion per year. The I-PUD is a mobile sensory device capable of detecting Stage-I pressure ulcers (bed sores) in human beings of all skin colors, while providing quantitative data and a graphical representation on a portable computer. This device will provide medical researchers at the University of Pennsylvania’s Department of Physical Medicine and Rehabilitation, the means of acquiring and documenting data corresponding to pressure ulcer diagnosis. This project of fabricating the I-PUD provides the undergraduate engineering students with hands-on experience in the real world research environment. The graphical user interface is coded using LabView 7.0 software. The purpose of the GUI is to display and record data from the I-PUD sensors. When the I-PUD is switched on, the user calibrates the photo sensor by getting the voltage corresponding to the reflectance from the inner forearm. Subsequently, reflectance is displayed in real-time on a graph as the difference between the reference value and the current value. Output from the temperature sensor is converted from volts to degrees Celsius and displayed in a gauge. Pressure is also displayed in a gauge, and if the pressure is above a given threshold, the GUI stops displaying data. The numerical data (in volts) is simultaneously tabulated and can be saved to disk.