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

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

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

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.

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

Chiari I Malformations

Valsalva Maneuver  Expiratory effort against a closed glottis  Increases pressure within the thoracic cavity

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

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

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

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

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

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

Preliminary Design 300 GWalls Transducer Amplifier ValveValve Control A/D D/A Computer Display P t

Mouthpieces Rigid Plastic Low dead space Disposable or easy to sanitize Tongue Depressing Rigid White w/ adapter SDIRigid White

Valves Balloon Shutter Auto

Transducers Manometers Diaphragm w/ strain gauge

Design Matrix - Valves AutoBalloonShutter MR Compatibility 351 Effectiveness344 Ease of Operation 441 Overall10136

Design Matrix - Mouthpieces Tongue Depressing SDIRigid White Size234 Rigidity335 Ease of Use145 Total61014

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

Future Work Construct prototype Conduct testing Research human subjects testing requirements

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

Questions?