Transcript No Slide Title

Quad Rat Vitals Monitor
Robert
1
Bjerregaard ,
Advisor: Paul
Matthew
1
Thompson ,
1
Bollom ,
Caitlyn
1
Collins ,
PhD. Client: Alex
Derek
1
Klavas
2
Converse ,
PhD.
1Department of Biomedical Engineering, 2Department of Medical Physics; University of Wisconsin - Madison
Final Design
Project Motivation
Our client’s current setup.
Picture taken in spring 2009.
Our client’s research requires him to
monitor four vitals of each rat
individually. The laboratory assistants
must be informed in a timely manner if
any of the four vitals enter critical ranges
so adjustments to the anesthesia can be
made.
Breathing Rate
• Force sensing resistor (Figure 1)
wired in series with 5V voltage
divider
• Velcro™ respiration belt (Figure
1) fabricated with ABS plastic
plate to help direct force from the
thoracic cavity onto FSR
Figure 1. Respiration belt (left) used in tandem
• Testing results yielded similar with FSR (right)
waveforms with and without the
respiration belt (Figure 2)
Figure 2. Comparison of voltage
data obtained by two different breath
detection methods. Top: FSR placed
on top of rat with respiration belt.
Bottom: FSR placed underneath rat
without respiration belt
voltage
The design and construction of a rat vitals-monitoring system is
essential for simultaneously monitoring multiple anesthetized rats. Our
client currently runs PET scans on four rats concurrently, and the scans
can last up to two hours. During the two hour scans, the rats are under
anesthesia and doses of the anesthesia medications must be adjusted
based on the rats’ vitals. The client desires to have an accurate, reliable,
and easy to use rat vital monitoring device to aid in this process. The
current design for this monitoring device includes force-sensing
resistors for monitoring breathing rate, thermistors to monitor rectal
temperatures, and pulse oximeters to monitor SpO2 levels and heart
rates. The design also includes an easy to read graphical user interface
(GUI) that displays running averages of the four vitals, histories graphs
of the four vitals, and live traces of heart rate and breathing rate. All
information is presented on a single screen, and data from each trial is
stored for further analysis.
Pulse Oximeter
• Circuit currently under construction by graduate student
• Photodiode & LED were excised from an existing Nellcor pulse
oximeter probe and mounted with heat shrink on a plastic clothespin
with a compromised spring (Figure 5).
• Testing was conducted on an anesthetized rat and data was collected for
processing as seen in Figure 6.
• More data is required to verify the accuracy of the pulse oximeter probe
voltage
Abstract
Figure 5. Modified pulse oximeter probe
with mounted LED’s and photodiode
Figure 6. Photodiode voltage versus
time after filtering in MATLAB
Graphical User Interface
Temperature
Existing Devices
• MouseOx, produced by Starr Life Science™ and the Nellcor N-100
• Monitor SpO2 levels, heart rate, and
MouseOx monitors breathing rate
• Not capable of monitoring multiple rats
MouseOx: Image taken from
• Four separate units not cost effective
http://www.starrlifesciences.com/images/products/
mouse_analog.png
Design Criteria
•SpO2 (±2%)
•Heart rate (up to 500 beats/min)
•Rectal temperature (33C - 38C)
•Respiration rate (20-30 breaths/min)
Figure 7. Screenshot of
actual LabVIEW GUI
Figure 3. Circuit consists of a
voltage divider and a non-inverting
operational amplifier.
Figure 4. Digital thermometers
purchased from local store modified
to measure rectal temperatures.
• Thermistor resistance varies linearly with temperature in
desired temperature range (~33C - 38C)
Future Work
Picture demonstrates use of thermistor and force plate.
Pictures taken November 30, 2009.
Picture demonstrates use of respiration belt.
•Integrate new pulse oximeter circuit
•Fabricate three additional pulse oximeter circuits and probes
•Prepare new computer for integration into final design
•Fabricate circuitry housing and print circuit boards
•Test device on rats during PET scans
• Data autosaves every 15 seconds
• Live traces of breathing and heart rate displayed
• Contains scalable history graphs of heart rate, breaths per minute,
temperature, and SpO2
• Displays current vital values
• Chart marker allows for easy follow-up analysis
Acknowledgements
We would especially like to thank Liz Ahlers, Tim Balgemann, Dr. Alex Converse, Peter Klomberg, Amit Nimunkar,
Professor Paul Thompson, Ph.D., and Professor John Webster, Ph.D., Nate Werbeckes
References
Webster, J. G., Design of Pulse Oximeters. IOP Publishing Ltd 1997.
Starr Life Sciences™ Corp. © 2009
Nellcor Puritan Bennett LLC. © 2009
Jack Ho, Joseph Yuen, Nate Werbeckes (Last semester’s team) accessed at
http://homepages.cae.wisc.edu/~bme300/rat_monitor_s09/