FATIGUE OF POLYMERS IN THE ROLLER HEAD RACEWAY OF EXTRACORPOREAL CIRCUITS DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctorate of Philosophy in the Graduate School of The Ohio State University by Allison Joan Bednarski Spiwak, M.S. ♦♦♦♦♦ The Ohio State University 2008 Dissertation Committee Approved by Professor Derek J Hansford, Adviser Professor Alan Litsky Adviser Professor Thomas Williams Biomedical Engineering Graduate Program ABSTRACT DYNAMIC FATIGUE OF POLYMERS IN THE ROLLER HEAD RACEWAY OF EXTRACORPOREAL CIRCUIT by Allison Joan Bednarski Spiwak, M.S. Polyvinyl chloride (PVC) is a brittle amorphous polymer, but processing the PVC with plasticizer results in a flexible material able to form non-rigid tubing. Plasticized PVC (pPVC) is available in medical grade products for use in extracorporeal drug and fluid delivery. There are known complications including plasticizer loss, drug interactions, spallation and raceway rupture associated with this product when used in the roller pump of the cardiopulmonary bypass circuit. This is pioneering research that studies tubing fatigued by use in the roller head raceway. The hypothesis states pPVC tubing exposed to the roller head raceway in a system simulating cardiopulmonary bypass changes material properties for tensile strength, elastic modulus and elongation. An additional hypothesis states spallation is recognized continually during compression in the roller head raceway and occurs at multiple surfaces of the tubing inner lumen. Better evaluation of polymers approved and chosen for the specific medical application of ii extracorporeal circulation by the roller head raceway and other approved devices will be obtained through this research protocol. With this basic knowledge clinicians will better understand the product selections available and better understand how to evaluate material offered from the manufacturers for specific applications. Minimal research recognizes the basic science of spallation and catastrophic rupture that occur during cardiopulmonary bypass. Cardiopulmonary bypass material selection was made to alleviate these concerns including the switch to pPVC from other non-rigid polymers, such as silicone and natural rubber. PVC is known to have a complicated morphology unstable during the compression in the roller head raceway. The initial phase of the study will trend the change in mechanical behavior of the polymer tubing after exposure to fatigue stresses of cyclic bending and compression by the roller head contact. This includes mimicking set-up and priming techniques used to prepare the equipment for patient care. Physiological saline and lipid will be used to duplicate the blood interaction with the pPVC known to influence material chemical stability. Pump settings for occlusion and RPM will simulate clinical cardiopulmonary bypass protocols. The material takes on a more crystalline structure leading to changes in the performance of the pPVC material. This simulation will develop the knowledge to understand the changes in behavior experienced during a typical cardiac surgical procedure. iii DEDICATION All our dreams can come true, if we have the courage to pursue them. -Walt Disney Mom and Dad everyday was like being at the Magic Kingdom. Barb, Chris, Marilyn, Louise and Alvin you told me I was a bonus, called me baby Zero and were always the best sisters and brother you could be. Steve, I owe you for the next 50 years. Alan, be courageous as you pursue your dreams. iv ACKNOWLEDGMENTS It is with great gratitude that I wish to recognize those that have supported my effort to complete my doctoral studies. Dr. Derek Hansford saw the light at the end of the tubing. He realized the importance the basic science of extracorporeal technology research. Drs. Alan Litsky and Tom Williams gave enthusiasm and support to see this work to completion. Drs. Kupprasamy, Agarwal and Hansford and their research staff provided expertise and access to equipment for laser particle counting, SEM and atomic force microscopy. Adam Pilchak PhC, Material Science Engineering, provided access and expertise with the mechanical behavior testing equipment. We took on our tasks, saw our goals and exceeded expectations. Mark Dumond, Anna Iulianelli, Nabil Nehaili, Drs. Robert Hamlin and Lynne Olson all stepped up to the “pump”. Dr. Larsen worked to maintain the Circulation Technology Division high academic, research and service standards. Kate Matusak worked hard to make sure we did what we needed to. The CT students have held several important roles in this pursuit. Stonerock, Grady, Sullivan, Warren, Leatherbury, Horbal, Gude, Hubbard, Melone and Preston all contributed to this work. The Classes of 2009 and 2010 trusted it would happen. v VITA July 14, 1971............................................................. Born – Independence, OH USA 2002............................................................................ M.S., Biomedical Engineering The Ohio State University 2000-2004 ................................................................. Circulation Technologist, Continuing Education Coordinator, Circulation Technology Division The Ohio State University 2004............................................................................ Instructor Circulation Technology Division The Ohio State University 2007 .......................................................................... Interim Director Circulation Technology Division The Ohio State University PUBLICATIONS Research Publications 1. Spiwak A, Horbal A, Leatherbury R, Hansford D. Extracorporeal tubing in the roller pump raceway: Physical changes and particle generation. JECT. 2008 Sep;40(3):188-92. 2. Goldstein AH, Monreal G, Kambara A, Spiwak AJ, Schlossberg ML, Abrishamchian AR, Gerhardt MA. Partial support with a centrifugal left vi ventricular assist device reduces myocardial oxygen consumption in chronic, ischemic heart failure. J Card Fail. 2005 Mar;11(2):142-51. 3. Riley JB, Beckley PD, Tallman RD, Spiwak AS. Successful use of a competency step exam in a perfusion education program. JECT 2006 Mar; 38(1):38-43. 4. Cassidy LK, Finney AS, Ellis WC, Spiwak AJ, Riley JB. Quantifying platelet gel coagulation using Sonoclot and Thrombelastograph hemostasis analyzer. JECT. 2005 Mar; 37(1):48-51. 5. Ellis WC, Cassidy LK, Finney AS, Spiwak AJ, Riley JB. Thrombelastograph (TEG) analysis of platelet gel formed with different thrombin concentrations. JECT. 2005 Mar; 37(1):52-7. Abstracts 1. Stonerock B, Grady K, Hansford D, Riley JB, Spiwak AJ. Roller Pump Fatigue in Coated vs. Uncoated PVC Tubing. Abstract. JECT 2006. 2. Phipps R, Garmon J, Riley JB, Spiwak AJ. Thermodilution Cardiac Output Simulator for Training and Troubleshooting. Abstract. JECT 2005; 37:114. 3. Goodrich D, Messer V, Spiwak A. Extracorporeal Circuit Fluid Dynamics and Fluid. Composition: The Effects of Thrombus Formation. Abstract. JECT 2005; 37:119. Editorials 1. Baker RA, Dickinson TA, Shann, KG, Likosky DS, Bednarski Spiwak A. Perfusion: Part of the Perioperative Blood Transfusion and Blood Conservation Management Team. Ann Thorac Surg. 2008 Jan; 85 (1):359. FIELDS OF STUDY Major Field: Biomedical Engineering Minor Field: Micro and Nano Technology Cardiovascular Instrumentation vii TABLE OF CONTENTS ABSTRACT...................................................................................................................II DEDICATION ............................................................................................................ IV ACKNOWLEDGMENTS ...........................................................................................V VITA............................................................................................................................. VI TABLE OF CONTENTS........................................................................................ VIII LIST OF FIGURES.................................................................................................... XI CHAPTER 1 INTRODUCTION ...............................................................................1 MOTIVATION AND GOALS .............................................................................................2 COMPLICATIONS OF CARDIOPULMONARY BYPASS....................................................4 CENTRIFUGAL PUMP......................................................................................................7 ROLLER PUMP ..............................................................................................................10 LUMEN CONTACT.........................................................................................................14 SILICONE TUBING.........................................................................................................16 PLASTICIZED POLY(VINYL CHLORIDE) USE IN MEDICINE ......................................17 DEHP.............................................................................................................................20 PLASTICIZED POLY(VINYL CHLORIDE) USE IN THE ROLLER PUMP.......................20 SURFACE MODIFICATIONS ..........................................................................................23 CHAPTER 2 HEART-LUNG MACHINE AND CARDIOPULMONARY BYPASS ........................................................................................................................25 PURPOSE........................................................................................................................25