MR Airway Pressure DeviceGroup MembersLaura SheehanKevin Johnson

Jon CappelNoelle Simatic

Client Dr. Victor Haughton

Advisor Prof. Mitch Tyler

AbstractAn airway pressure device was designed for use in an MR imager. This device will assist our client in studying CSF flow during Valsalva maneuvers performed by children with Chiari I malformation. Current research suggests that CSF flow decreases during Valsalva maneuvers in these patients. The final product consists of a rigid mouthpiece, pressure transducer, and compressed air operated valve system.

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• Current devices are not MR

compatible

Problem Statement

• Our client needs a device to monitor exhalation pressure exerted during a Valsalva maneuver– Specifically for studying CSF flow – Images of the spine will be taken using MR imaging

• Research will be focused on children with Chiari I malformation– Current studies show that CSF flow decreases during

Valsalva maneuvers in these patients– This causes patient symptoms to worsen

• Pressure measurement would be beneficial for data analysis and accuracy

Client Specifications

Needs to be MR compatiblePressure must be measured from beginning

of Valsalva through mid expirationSmall to minimize dead air spaceUsable by both alert and anesthetized

patients

Device to measure airway pressure during Valsalva maneuver in pediatric patients with Chiari I malformations

Chiari I Malformations

http://www.chiariclinic.org

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

cavity

http://www.valsalva.org

MR Requirements• Utilizes strong

magnetic fields (1-3 T)• Non-magnetic

materials• No metal touching the

patient• Must not affect image

quality• Comply with

geometric constraints of GE Signa scanners and single channel head coil

Final DesignComponents• Rigid mouthpiece• Silicon diaphragm pressure transducer• End cap with tubing barb

Features• Device can be autoclaved – Transducer can be sterilized

• Functions using compressed air and vacuum• Device is small to minimize dead air space• Can be used during normal breathing as well as

during a Valsalva maneuver

Testing• Device was calibrated using a manometer• 3 members of our design team served as

subjects for volunteer testing• Maximum pressure during Valsalva was

recorded• Data was acquired using Labview and

graphed in Matlab• Additional testing was performed in the

MR suite at the Waisman Center

Results• Subject was able to breathe normally and

perform Valsalva using the device• Device can withstand a pressure of at

least 90 mm Hg– Typical child maximum airway pressure is 60

mm Hg• Device was found to be MR compatible

and is easy to operate

Future Work• Obtain a 3-way valve for compressed air

and vacuum supply• Construct alternative prototype with

balloon valve for comparison• Research human subjects testing

requirements

Acknowledgements We would like to thank the following

individuals for their assistance this semester:– Dr. Haughton, Department of Radiology– Professor Tyler, Department of Biomedical

Engineering–Matt O’Brien, Pulmonary Function Lab– Rick and Larry, ECB Machine Shop