Thermistor Temp. (°C) Thermometer Temp. (°C) Thermistor Temp. vs. Thermometer Temp. Figure 1. Salter Labs ThermiSense ® [3] Figure 2. Thermistors measuring flow [2] Figure 3. Cannula for Pressure & ETCO 2 [3] Combined Thermistor, Pressure, and ETCO 2 Device for Use in a Sleep Laboratory Lindsey Carlson, Nicole Daehn, Robyn Hrobsky, Jason Tham Client: Dr. Christopher Green, Department of Pediatrics, University of Wisconsin Hospital Advisor: Professor Willis Tompkins, Department of Biomedical Engineering, University of Wisconsin Thermistor Distance Test: Compared measured signal amplitudes versus device distance from nasal airway Verified breath detection if cannula is removed from direct airflow Prototype demonstrates proof of concept Exhibits efficacy of thermistor mounted cannula Device compatible with existing equipment 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 Design selected based on disposability, accuracy, and cost Uses Salter Lab 5055 oral/nasal cannula Measures ETCO 2, nasal pressure, and temperature change via thermistors Three 10 kΩ wire lead 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 4. Final design. Figure 5. Voltage vs. Time for resting respiratory rate. Final Design Testing and Results Conclusions References Acknowledgements [1] Dallas Center for Sleep Disorders. Pediatric Sleep Apnea. Retrieved from sleep.com/pediatric-sleep-apnea.php [2] Rochester Sleep. Ultra Flow Respiration Monitors. Retrieved from [3] Salter Labs. Growing Steadily on a Quality Foundation. Retrieved from Device Specifications Measure air flow, pressure, and ETCO 2 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 ETCO 2 measurements into one device, sampling from both nostrils and the mouth, and attaching in both a durable and comfortable fashion. 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 Sleep Disordered Breathing Abstract Competition Competition requires expensive, non-disposable thermistors Testing and Results Thermistor Comparison Test: Compared Pro-tech thermistor to prototype Evaluated varied tidal volumes and respiratory rates (i.e. resting, deep and slow, shallow and fast) Counted number of detected breaths for each device Prototype. Pro-tech thermistor. Table 1. Average Signal Amplitudes for Prototype and Pro-Tech Thermistor at al distances Distance (mm) Average Amplitude of Prototype (mV peak-to-peak) Average Amplitude of Pro-tech thermistor (mV peak-to-peak) Thermistor Temperature Test: Quantitatively correlate changes in thermistor resistance to ambient temperature Average resistance change for each degree temperature change was kΩ/°C Figure 6. Thermistor Temp. vs. Thermometer Temp.