Amplified voltage across thermistors during normal breathing

1. Combined Thermistor, Pressure, and ETCO2 Device for Use in a Sleep LaboratoryLindsey 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 Figure 2. Thermistors measuring flow [3] Figure 3. Cannula for Pressure & ETCO2 [4] 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 http://www.dallas-sleep.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/ 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