April 9, 2004 BME 272/273 1

Investigation of Bubble Formation in Tuohy-Borst Adaptors

Department of

Biomedical Engineering

Melanie Bernard, Isaac Clements, & Jason Hirshburg

Advisor: Ted Larson III, M.D.

April 9, 2004 BME 272/273 2

Problem Statement• Bubbles are seen within the Tuohy-Borst Adaptor

– Origin/cause unknown

• Consequences– Can get stuck in small arteries, inhibiting blood and oxygen to the brain– Causes stroke in 0.1% of procedures (bubbles > 1ml)

• Accessory Problems– Bubbled are hard to remove; they stick to inner surface of tubing/adaptor– Occurs in adaptors of different length, angle of arm– May be from multiple sources

http://www.cookurological.com/products/ureteroscopy

April 9, 2004 BME 272/273 3

Problem Definition• Find the cause of the bubbles and correct it!– 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 introducing new ones

– Limitations• Time – 6 months• Money – have only a

reasonable budget.• Equipment – don’t have access to blood or ultra- sound machines

www.urmc.rochester.edu/strong/ cardio/cathlab.htm

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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 by Dr. Larson).

• Dr. Larson reverses flow 3 times without bubbles before proceeding.

www.angiodynamics.com

April 9, 2004 BME 272/273 5

Background cont.• Bubble Traps– Used when blood is

routed outside the body with pumps

• Cost Analysis– $45k/procedure

• $25k Radiology• ~4-6 min. to clear bubbles• ~3 hour procedure• =$700!!

http://www.laboratoryglassapparatus.com/parts_bubbletrap.gif

http://www.convergenza-online.com/dbt.htm

April 9, 2004 BME 272/273 6

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

– Could save up to $700 per procedure (not including saving money that would be lost for inducing a stroke)

April 9, 2004 BME 272/273 7

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

April 9, 2004 BME 272/273 8

Previous Work• Observed device in a medical

procedure on 11/18/03

• Literature Search

• Innovation WorkBench (revised 3/2)

• Conducted experiments– Primary: tested equipment– Secondary: simulated pressures

and temperatures of entire system

– Tertiary: testing individual components to different conditions

• Filmed procedures on 2/2/04 and 3/31/04; obtained new supplies

• Performed calculations based on actual and worst-case scenario parameters

April 9, 2004 BME 272/273 9

Possible Sources of Bubbles1. Leaks

From 3-way valve

From rotating hemostatic valve

Between adaptor and catheter

2. Introduced during adjustments

In flushing process

Injecting contrast agent

Reversing fluid flow

3. AdaptorAngle of arm causes local pressure dropMicrobubbles pool at connections

4. Temperature differences

N2, O2, or CO2 coming out of blood

Air coming out of saline

5. Initial flushing processIn catheterIn saline tubePulling back saline syringe

6. SalineAir coming out of solutionPushed into system by pressure bagHigh flow rate and interaction with bloodPressure drop from 250 – 0 mmHg

7. Pressure change for N2, O2, & CO2 in blood

Local pressure drop at diameter change

Pressure drop across catheter

Pressure drop from 100 – 0 mmHg

April 9, 2004 BME 272/273 10

Experiments Conducted• Primary 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

• Tertiary Experiments:– Tested connections for leaks

• 35 degree catheter turn

– Air solubility in saline under pressure (250 mmHg)

– Tested catheter for bubbles after flushing

– Tested bubble occurrence after syringe pull-back

April 9, 2004 BME 272/273 11

Videotaping the proceduresWe videotaped the bubble phenomenon during two actual procedures in Dr. Larson's operating room:

The first videotape was created on 2/24/04 with a standard VHS video camera.

We acquired a high resolution digital video camera to videotape a second procedure on 3/31/04.

April 9, 2004 BME 272/273 12

Videotape Analysis

Observations:

•There are many bubbles forming!

•Out of 4 minutes of footage, we recorded 15 bubble occurrences.

•Bubbles appear to be coming from within the catheter

•In 14 out of 15 cases, the bubbles appear under set conditions:

1. Saline is flowing forward into the catheter

2. The 3-way valve is opened and flow is reversed

3. Bubbles appear immediately and seem to be coming from within the catheter.

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Current & Future Work

• In a meeting with Dr. Larson, we laid out our final goals for the project, including:– Determining all possible sources of bubbles – Ruling out as many as possible through our observations,

calculations, and experiments.– Taking the remaining possibilities and determining the

likelihood of each theory.– Create a final analysis of the most likely cause.– Give suggestions for improving the situation.

• We have researched the following catheter clearing methods:– Wetting agents– Dynamic Bubble Traps (DBTs)– Degassing saline before injection (and heat?)

April 9, 2004 BME 272/273 14

Acknowledgements

Dr. Ted Larson and staff Dr. Paul King

Dr. Joan WalkerDr. Robert RoselliDr. Todd Giorgio

Dr. Cynthia PaschalDr. Rick HaseltonDr. Bob Galloway

Matt Lytle for his services as cameraman.

We would like to thank the following professionals and experts for their input:

April 9, 2004 BME 272/273 15

BibliographyCatheter Flushing, Bubble Formation within Catheters, Dynamic Bubble Traps, Wetting Agents:

http://www.ajnr.org/cgi/content/full/22/4/709http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=

http://www.convergenza-online.com/dbt.htmhttp://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=/

http://www.bandwidthmarket.com/resources/patents/apps/2001/5/20010001111.html

Manufacturing Links for Tuohy-Borst Adaptors:http://www.cordis.com/logc/active/crdus/en_US/html/cordis/downloads/Product_Catalog.pdf

http://www.cookurological.com/products/ureteroscopy/5_06/5_06_06.htmlhttp://www.fda.gov/ohrms/dockets/ac/03/briefing/3993b1_CLiRpath-peripheral-IFU-revE-10.pdf

 Images for Catheter Insertion Procedure:

http://www.angiodynamics.com/tips.htm 

Interventional Neuroradiology Links:http://www.csmc.edu/2725.html

http://neurosurgery.mgh.harvard.edu/interventional/http://www.okxray.com/aneurysm_coiling.htmhttp://www.emedicine.com/radio/topic870.htm

http://www.carotidarterystenting.com/Articles/Article1.htm 

April 9, 2004 BME 272/273 16

Questions…?

Visit our website at http://vubme.vuse.vanderbilt.edu/srdesign/2003/group17/

www.cookurological.com/.../ureteroscopy/ 5_06/5_06_06.html