Testing System for a Pressure Sensitive Cardiovascular Catheter Dec. 13, 2006 Team Members: Danielle Ebben Erik Yusko Anthony Wampole Anita Zarebi Client: Colette Wagner Nancy Sweitzer, M.D., Ph.D. Advisor: Professor William Murphy2 Table of Contents I. ABSTRACT ...................................................................................................................................................... 3 II. PROBLEM STATEMENT.............................................................................................................................3 III. BACKGROUND ............................................................................................................................................3 IV. DESIGN CONSTRAINTS ........................................................................................................................... 4 V. PRELIMINARY DESIGN ALTERNATIVES............................................................................................. 5 I. DESIGN ALTERNATIVE #1: PLUNGER DESIGN ............................................................................................ 5 II. DESIGN ALTERNATIVE #2: BALLOON .......................................................................................................... 6 III. DESIGN ALTERNATIVE #3: ROTATING CYLINDER ..................................................................................... 7 VI. ANALYSIS OF DESIGN OPTIONS ......................................................................................................... 9 VII. FINAL DESIGN ..........................................................................................................................................10 VIII. FUTURE WORK .......................................................................................................................................11 IX. ETHICAL CONSIDERATIONS................................................................................................................12 X. CONCLUSION..............................................................................................................................................12 XI. REFERENCES ............................................................................................................................................14 APPENDIX A: PRODUCT DESIGN SPECIFICATION (PDS) ...............................................................15 APPENDIX B: LIST OF MATERIALS ........................................................................................................18 APPENDIX C: ACKNOWLEDGMENTS ....................................................................................................193 I. Abstract Blood pressures within the heart and surrounding vessels are often measured using catheters that are equipped with pressure transducers. The accuracy of blood pressure measurements from these catheters has been called into question as calibration data is not provided by the manufacturer. A product is needed to calibrate and verify the pressure transducer measurements while simulating in vivo conditions. A product is being developed to encase the catheter in saline solution while achieving pressures up to 200mmHg. An air pump increases pressure in the chamber through manual or micro-controller control. Pressure in the chamber is monitored with an additional pressure transducer imbedded in the tank. In a second-generation prototype a feedback loop will pressurize the chamber to a value specified by the user via a pressure sensor, micro-controller, and air pump. II. Problem Statement Internal blood pressures within the heart and surrounding vessels are typically measured with catheters that are equipped with pressure transducers. Properly calibrated catheters are required to ensure valid blood pressure measurements during diagnosis and clinical trials. Current calibration techniques are thought to be unreliable. A product is needed to calibrate and verify catheter pressure transducer measurements while simulating in vivo conditions. III. Background The traditional process of catheter use in cardiovascular surgery begins with a one hour evaluation of the patient’s heart and body. After consent for surgery is granted, the catheter is guided into the heart via the femoral artery and aorta (Figure 1). A drug is then administered to lower the pressure within the heart’s walls. Finally, pressure measurements are obtained with the catheter. Clinical trials are being conducted by our client to verify a new blood pressure monitoring technology. The pressure readings of the new technology are compared to those given by the catheter and EKG. The readings between these devices are expected to be nearly identical (within 2 mmHg). However, Figure 1: The catheter is inserted into the aorta and guided into the heart [1].4 a significant amount of drift and inconsistency in the catheter’s pressure readings has been observed, particularly at pressures near 200 mmHg [2]. First attempts to address this problem began with our client directly contacting Millar Instruments, the catheter manufacturer. After hearing the problem, Millar Instruments sent a new catheter to our client, stating that the problem would be fixed with a new catheter. During correspondence, our client often inquired as to what the validation and verification process for the catheter consisted of and Millar Instruments offered no response. Because of this, our client felt the need to develop her own method of verifying the catheter’s accuracy and presented the problem to our team [2]. Our client had previously employed a student to address this problem, but the device and process they came up with was not satisfactory. A general schematic of this device is shown in Figure 2. Our client is dissatisfied with this design for several reasons. The valves that were supposed to close behind the catheter and secure it in place within the tube were leaky. This makes the design messy and the pressure readings inconsistent and inaccurate. Even when the device was working as it should, constant pressure readings were still not observed, making the design ineffective in meeting the needs of our client. IV. Design Constraints Millar Instruments’ current techniques for calibrating the catheter are unknown. Therefore, until a testing system is designed that validates the accuracy of the catheter’s
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