1. Device Specifications Sleep Disordered Breathing
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
Device Specifications
Testing and Results
• 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 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
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 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 [2] Davey, Margot. The Royal Children’s Hospital of Melbourne.  Sleep Studies. Retrieved from [3] Rochester Sleep. Ultra Flow Respiration Monitors. Retrieved from [4] Salter Labs. Growing Steadily on a Quality Foundation. Retrieved from
Figure 2. Thermistors measuring flow [3]
Figure 3. Cannula for Pressure & ETCO2 [4]
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