Transcript Document

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.