Transcript Device to Improve Diagnostic Yield of Fine Needle

Combined Thermistor, Pressure, and ETCO2 Device for
Use in a Sleep Laboratory
Lindsey Carlson, Nicole Daehn, Jack Page, Robyn Hrobsky
Client: Dr. Christopher Green, Department of Pediatrics, University of Wisconsin Hospital
Advisor: Professor Willis Tompkins, Department of Biomedical Engineering, University of Wisconsin
Abstract
Current methods of polysomnography can lead to
inaccurate measurements, discomfort, and sleep
disruption. The goal of this project is to design and
develop a prototype that combines breath,
pressure, and ETCO2 measurements into one
device, sampling from both nostrils and the mouth,
and attaching in both a durable and comfortable
fashion.
Sleep Disordered Breathing
•
•
•
•
Affects 18 million Americans
10 million of which remain undiagnosed [1]
Disrupts sleep hundreds of times each night
Can lead to:
• Behavior, emotional, social problems
• Delayed mental/physical growth
Polysomnography
•
•
•
•
Sleep Study
Brain Activity
Muscle movements
Respiratory effort
O2 Saturation
Device Specifications
• Measure air flow, pressure, and ETCO2 from both
nostrils and mouth
• Disposable
• Device should fit pediatric patients
• Should stay on patient throughout the duration of a
sleep study (~8 hours)
• Comfortable, durable, and limit sleep disruption
• Be compatible with existing equipment
Testing and Results
• Amplified voltage across thermistors during normal
breathing
• Tested with surface mount and wire lead thermistors
• Used LabView to obtain real-time voltage vs. time
data
• Qualitatively analyzed for breath detection
• Additional testing on thermistors within normal
breathing temperature range
Final Design
Design selected based on disposability, accuracy, and cost
• Uses Salter Lab 5055 oral/nasal cannula
• Measures ETCO2, nasal pressure, and temperature
change via thermistors
• Three 10 kΩ surface mount thermistors mounted to
each nasal/oral extension
• 2” x 0.6” silicone attachment pieces on either side of
cannula prongs
• Thermistor wires fixed to cannula tubing
• Low cost ensures disposability
Figure 5. Voltage vs. Time of wire lead thermistor (left) and surface mount thermistor (right)
Future Work
• Order GrassLead Safety Connectors for thermistors
• Test the prototype in the Sleep Lab
• Work with manufacturer to produce device commercially
Figure 1. Pediatric Sleep Study[2]
References
Three measurements from each breath
• Airway Pressure
• End Tidal CO2
• Flow
[1] Dallas Center for Sleep Disorders. Pediatric Sleep Apnea. Retrieved from http://www.dallassleep.com/pediatric-sleep-apnea.php
[2] Davey, Margot. The Royal Children’s Hospital of Melbourne. Sleep Studies. Retrieved from
http://www.rch.org.au/sleep/studies.cfm?doc_id=5040
[3] Rochester Sleep. Ultra Flow Respiration Monitors. Retrieved from
http://www.rochestersleep.com/Respiration.htm
[4] Salter Labs. Growing Steadily on a Quality Foundation. Retrieved from
http://www.salterlabs.com/
Figure 4. Final design.
Figure 2. Thermistors measuring flow [3]
Figure 3. Cannula for Pressure & ETCO2 [4]
Acknowledgements
Dr. Christopher Green, Professor Willis Tompkins, Professor Steve Weber, Sleep Lab staff,
Amit Nimunkar, University of Wisconsin Hospital, University of Wisconsin-Department of
Biomedical Engineering