March 24, 2004BME 272/2731 Investigation of Bubble Formation in Tuohy-Borst Adaptors Department of Biomedical Engineering Melanie Bernard, Isaac Clements, & Jason Hirshburg Advisor: Ted Larson III, M.D.

March 24, 2004BME 272/2732 Problem Statement Bubbles are seen within the Tuohy-Borst Adaptor –Can get stuck in small arteries in brain, inhibiting the supply of blood and oxygen –Causes stroke and death (1ml) –Once present, bubbles are difficult to remove because they stick to inner surface of system –Occurs in adaptors of different geometries

March 24, 2004BME 272/2733 Problem Definition Constraints –Solution must apply to all adaptor types –Any system changes must not significantly change adaptor cost or the catheterization procedure. –Must eliminate problem without having other detrimental effects. Limitations –Time –Money –Equipment cardio/cathlab.htm

March 24, 2004BME 272/2734 Background Dr. Larson has 15 years of experience in interventional neuroradiology Catheter uses: –Angiography –Embolization of arteriovenous fistulas –Aneurysms –Preoperative embolization of neck and intracranial tumors Bubbles are consistently observed in catheterization procedures (but have not been formally documented).

March 24, 2004BME 272/2735 Primary Objective Our task is to discover the cause of bubble formation and correct it Observations from Dr. Larson’s procedures: Bubbles… –Up to 10-20% of tube diameter –Stick to inner surface of adaptor –Appear at the edge of the Y-junction –Occur before microcatheter is inserted –Typically occur when catheter flow is reversed and blood hits the edge of the Y-junction and interfaces with the saline (or contrasting agent)

March 24, 2004BME 272/2736 Market Potential Target group –Operating rooms worldwide Will meet customer needs –Catheterization procedures will be safer Is technologically feasible –Physical principles and/or methods can be changed to eliminate bubble formation Is economically viable –Adaptor costs should not rise after our changes

March 24, 2004BME 272/2737 Previous Work Observed device in a medical procedure on 11/18/03 Literature Search Innovation WorkBench (revised 3/2) Conducted flow experiments with colored water and actual adaptor and tubing. Observed device in a second medical procedure on 2/2/04 and obtained new supplies Conducted more rigorous flow experiments, using realistic temperatures and pressures.

March 24, 2004BME 272/2738 Previous Experiments Preliminary Experiments: –Observed many bubbles throughout system Secondary Experiments: –Blood pressure = 120/80 (mmHg) –Saline pressure = 250 mmHg –Blood temp = 98.6 F –Saline temp = room

March 24, 2004BME 272/2739 Current Work We videotaped the bubble phenomenon during an actual procedure in Dr. Larson's operating room on 2/24/04. Observations: There are many bubbles forming! Bubbles appear to be coming from within the catheter They occur in several different scenarios Occur mainly in first few minutes of procedure

March 24, 2004BME 272/27310 Current Work (continued) Based on what we have observed in the video, we are currently researching bubble occurrence within catheters and different flushing procedures. A study conducted by the Dartmouth-Hitchcock Medical Center found that air is very likely injected frequently during catheter flushing and by individuals at all levels of training. We are researching the following catheter clearing methods: Wetting agents Dynamic Bubble Traps (DBTs) Degassing before saline injection

March 24, 2004BME 272/27311 Future Work Meeting with Dr. Larson this week to: –Observe his catheter flushing technique –Videotape another procedure from multiple angles with tripods –Discuss the results of our most recent literature search –Plan new experiments to test catheter flushing procedures

March 24, 2004BME 272/27312 Acknowledgements Dr. Ted Larson and staff Dr. Paul King Dr. Joan Walker Dr. Robert Roselli Dr. Todd Giorgio Dr. Cynthia Paschal Dr. Rick Haselton Dr. Bob Galloway We would like to thank the following professionals and experts for their input:

March 24, 2004BME 272/27313 Bibliography Catheter Flushing, Bubble Formation within Catheters, Dynamic Bubble Traps, Wetting Agents: Manufacturing Links for Tuohy-Borst Adaptors: Images for Catheter Insertion Procedure: Interventional Neuroradiology Links:

March 24, 2004BME 272/27314 Questions…? Visit our website at 5_06/5_06_06.html