Combined Thermistor, Pressure, and ETCO2 Device for Use in a Sleep Laboratory Lindsey Carlson, Nicol

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Combined Thermistor, Pressure, and ETCO2 Device
for Use in a Sleep Laboratory Lindsey Carlson,
Nicole Daehn, Jack Page, Robyn HrobskyClient
Dr. Christopher Green, Department of Pediatrics,
University of Wisconsin HospitalAdvisor
Professor Willis Tompkins, Department of
Biomedical Engineering, University of Wisconsin
Testing and Results
Device Specifications
Abstract
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
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.

• 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

Sleep Disordered Breathing
Final Design

• 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

• 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 k? 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

Polysomnography
Figure 5. Voltage vs. Time of wire lead
thermistor (left) and surface mount thermistor
(right)
Future Work

• Sleep Study
• Brain Activity
• Muscle movements
• Respiratory effort
• O2 Saturation

• Order GrassLead Safety Connectors for thermistors
• Test the prototype in the Sleep Lab
• Work with manufacturer to produce device
  commercially

Figure 1. Pediatric Sleep Study2
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.dallas-slee
p.com/pediatric-sleep-apnea.php2 Davey,
Margot. The Royal Childrens Hospital of
Melbourne.  Sleep Studies. Retrieved from
http//www.rch.org.au/sleep/studies.cfm?doc_id504
03 Rochester Sleep. Ultra Flow Respiration
Monitors. Retrieved from http//www.rochestersleep
.com/Respiration.htm4 Salter Labs. Growing
Steadily on a Quality Foundation. Retrieved from
http//www.salterlabs.com/
Acknowledgements
Figure 4. Final design.
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