MR Airway Pressure Device

1. MR Airway Pressure Device Group Members Laura Sheehan Kevin Johnson Jon Cappel Noelle Simatic Client Dr. Victor Haughton Advisor Prof. Mitch Tyler

3. Overview • Motivation • Problem Statement • Client Specifications • Background Information • Commercially Available Devices • Preliminary Design • Design Components • Mouthpiece • Valve • Transducer • Future Work

4. Motivation • Dr. Haughton is radiologist at UW-Hospital with a specialty in neuroradiology • Research interest in CSF disorders • Device needed to measure airway pressure during MR imaging

5. Problem Statement Our client Dr. Haughton is currently studying CSF flow during Valsalva maneuvers performed by children with Chiari I malformations. Current research suggests that CSF flow decreases during Valsalva maneuvers in these patients. The airway pressure device would help monitor the exhalation force exerted by each child during a Valsalva maneuver in the MR suite. Knowing the pressure exerted by each patient in the study would be extremely beneficial for data analysis and accuracy.

6. Client Specifications • Device to measure airway pressure during Valsalva maneuver in pediatric patients with Chiari I malformations Needs to be MR compatible Pressure must be measured from beginning of Valsalva through mid expiration Small to minimize dead air space Usable by both alert and anesthetized patients

7. Chiari I Malformations http://www.chiariclinic.org

8. Valsalva Maneuver • Expiratory effort against a closed glottis • Increases pressure within the thoracic cavity http://www.valsalva.org

9. Available Devices • Generally assess lung health • Use differential pressure transducer • Not usable in the MR environment • Examples: Images Courtesy of Viasys Healthcare

10. MR Background B0 Head N N S S • Main Field No Ferromagnetic Materials

11. MR Background RF Head N N S S • Main Field No Ferromagnetic Materials • Excitation RF No metal touching patient

12. MR Background N N S S • Main Field No Ferromagnetic Materials • Excitation RF No metal touching patient • Gradients  Everything must be shielded

13. MR Background RF N N S S • Main Field No Ferromagnetic Materials • Excitation RF No metal touching patient • Gradients  Everything must be shielded • Readout RF  Must not effect

14. Preliminary Design Transducer Measures Pressure Valve Closed during Valsalva Mouthpiece Disposable Interface

15. Preliminary Design Valve Valve Control A/D D/A Computer Transducer Display Amplifier P t 300 G Walls

16. Mouthpieces • Rigid • Plastic • Low dead space • Disposable or easy to sanitize Rigid White w/ adapter Tongue Depressing SDI Rigid White

17. Valves • Balloon • Shutter • Auto

18. Transducers • Manometers • Diaphragm w/ strain gauge

19. Design Matrix - Valves

20. Design Matrix - Mouthpieces

21. Potential Problems • Potential artifacts • Shielding equipment • Valve performance • Accuracy of pressure measurements • Data processing and output

22. Future Work • Construct prototype • Conduct testing • Research human subjects testing requirements

23. Acknowledgements • Thanks to . . . • Dr. Haughton • Prof. Tyler • Matt O’Brien, Pulmonary Function Lab

24. Questions?