Dalhousie University Senior Design Project Magnetic and articulating (MNA) Bougie assisted breathing tube placement during intubation Group Members: Chris Cloney Laura Hadley brian joseph Ian Westhaver Supervisor: Dr. Ted Hubbard Clients: dr. Andrew Milne1,2, dr. Dennis Drapeau1 1 Department of anesthesia – Dalhousie university 2 School of Biomedical Engineering – Dalhousie University Group #7 Dalhousie University Senior Design Project

Overview Introduction Requirements Methodology Testing and Initial Design Final Design Results Future Plans Adapted from Fong 2004 [1]

Introduction to Standard Intubation Current Devices Breathing tube Laryngoscope Technique Achieve visualization Insert breathing tube 15-17,000 intubations per year (QEII – anesthesia department )

Design Problem Difficult Intubation: 2-3% of all intubations (300 – 500 per year) Design and construct a device to use with a video laryngoscope to insert a breathing tube in difficult intubation scenarios. Introducing Bougie

Design Requirements Requirement Result Medical grade materials Disposable or easily sterilized Portable, volume less than 3500 cm3 Light, weigh less than 3 kg 1-2 attempts to introduce breathing tube Less than 25 seconds

Design Methodology Mechanical devices Magnets Difficult to use Intuitive Allows for fine motion

Testing – Distance X Minimum distance required for attraction Error bars at 95% confidence (3 trials) Minimum attraction distance between small magnet and large ceramic magnet. It was determined that a magnet with the strength of at least 6 ceramic magnets should be used.

Testing – Forces X Minimum separation force Error bars at 95% confidence (5 trials) Force required to pull magnets off of a steel beam. This standard test case is used to size commercial magnets for purchase.

Key Features Bougie External magnet Magnetic tip attracted into trachea Flexible tip to encourage articulation In conjunction with video laryngoscope External magnet Attracts magnetic bougie tip Varying force Controlled by anesthesiologist or anesthesiologist's assistant

Initial Design Bougie External magnet Tip not rigid enough Tip connection is too delicate MAGNET External magnet Cumbersome Imprecise control The initial bougie design featured a magnet tip on a cord with an inflatable chamber. The magnet tip would be attracted to the external magnet and guided into the trachea, and the chamber would be inflated. This inflation would effectively lengthen the bougie. The breathing tube is then guided into the trachea using the bougie and the bougie is removed. We found that the tip was too flexible, and the likelihood of the magnet becoming detached was too high. From this, a tip that is softer but not completely flexible is needed. The initial external magnet design featured a magnet attached to a cam follower to be placed on the patient’s neck. The magnet would attract the internal magnet into the trachea. The force of the external magnet applied to the internal magnet is adjusted by the cam mechanism. We found that this device hindered the intubation procedure, and so a smaller device is needed. MAGNET

Final Design Two Components External magnet moves flexible bougie tip Interior bougie External magnet moves flexible bougie tip From this our final design features a handheld external magnet, and a bougie with a magnetic and flexible tip, and a balloon.

Final Design – Bougie Magnetic Tip Balloon Connection

Final Design – Bougie Balloon Inflated by syringe Coarse articulation 50 mm

Final Design – Bougie Connection Joins flexible end to stiffer bougie shaft Flexible material allows for greater tip articulation

Final Design – Bougie Tip Magnet encased by flexible tip Fine articulation

Final Design – Magnet

Final Design – Magnet Shell Can be disassembled for cleaning

Final Design – Magnet Magnet 1-1/2” dia. x 1/4” thick 50 N

Final Design Implementation Magnetic Tip (Yellow) Flexible Tip (White) Balloon (Orange) Trachea (Green) Esophagus (Red) Lung (Pink)

Safety Sterilization No detachable parts Forces Disposable bougie Casing easily disassembled No detachable parts Forces Cricoid pressure (30–40 N) [3] Less than 10 N Error bars at 95% confidence (3 trials)

Results Requirement Result Medical grade materials Plastics Disposable or easily sterilized Both Portable, volume less than 3500 cm3 < 500 cm3 Light, weigh less than 3 kg < 0.5 kg 1-2 attempts to introduce breathing tube TBD Less than 25 seconds

Future Plans Construction of first iteration of final design by Jan 31st Testing completed through month of February Usability of external design Forces directly on vocal cords Possible cadaver testing Iteration of design and final construction

Questions? Acknowledgments References We would like to thank our clients Dr. Andrew Milne and Dr. Dennis Drapeau for their time and insight on this project. We would also like to thank our supervisor Ted Hubbard for the direction and intuition provided for this project. References [1] Sally Fong. 2004. Intubation. Retrieved from http://www.aic.cuhk.edu.hk/web8/Intubation.htm [2] Rassam, S., Wilkes, A., Hall, J., Mecklenburgh. 2005. A comparison of 20 laryngoscope blades using intubating manikin: visual analogue scores and forces exerted during laryngoscopy. Anaesthesia 60:384-394 [3] Vanner, R. 1992. Tolerance of cricoide presure by conscious volunteers. International Journal of Obstetric Anesthesia. 1:4:195-198

Medium Testing