1. Multifunction IV Catheter Brett Byram 1, Steve Harris 1, Adam Travis 1 Advisors: Gary Byram, Ph.D. 2 ; Paul King, Ph.D., P.E. 1 1 Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 2 MedTG LLC, Naperville, IL Intravenous (IV) Delivery and Sampling: The Problem… Patient IV injection and blood sampling create need for multiple needle sticks Blood sampling is essential for fluid monitoring, so sticks are unavoidable Patient experiences excessive invasiveness Unnecessary waste, disposal is a safety issue Solution: Incorporate blood sampling lumen into IV delivery catheter, prevent multiple punctures Concept: catheter with two lumen (injection and blood draw), with the exit points separated so that UNDILUTED blood samples can be drawn Acknowledgments Gary Byram, Ph.D.; Ben Close; Thomas Hall; Paul King, Ph.D.; Todd Giorgio, Ph.D.; Michael Miga, Ph.D.; Meghan Rice; Management of Technology - Marketing Multiple Lumen IV Catheter…a Solution? Blood draw lumen “stacked” on injection lumen, Figure 2 Use dual lumen catheter with reusable pump system to allow controlled simultaneous blood draw and fluid delivery Superior solution because IV administration is uninterrupted for blood draw, and only one unit is necessary for both functions Blood draw lumen IV administration lumen Patent and Market Potential Device Aspects and Safety Issues General physical and functional attributes will be same as a normal catheter Device lifetime: disposable 4-7 days after use (based on normal catheter lifetime) No new safety concerns in addition to typical concerns of normal catheter Hospital regulations prohibit interruptions to IV fluid delivery, RN’s will not halt fluid delivery without express consent from a physician Must control x-distance (distance between lumen ports, Figure 10) so that continuous IV injection does not contaminate blood draw Figure 1: IV injection and blood draw in brachial vein of the arm Figure 2: Concept drawing of multi-lumen catheter with cross-sectional drawing X Figure 10: Concept CAD illustration of the catheter with pump system Patents already exist for multiple lumen catheters, but these are designed for dual injection MedTG has a patent pending for this idea (Application No. 10/137, 186) Disposable medical device industry is about 48.6 billion dollars a year, and catheters/infusion devices comprise 39.1% of the market Physical Model Figure 4: Physical testing system Goal – to simulate the performance of the multifunction dual lumen IV catheter using a physical flow model Figure 4 shows the physical system used to simulate the functionality of the dual lumen catheter design. A peristaltic pump was calibrated to simulate a venous blood velocity of 4 cm/s. The water reservoir was elevated to induce a pressure in the system of 1.5 kN/m 2. Sugar was added to the water to increase the viscosity to 3 cP, which approximates blood. Two lumens were present in the tube, one to simulate blood draw, and the other to simulate fluid delivery. Needles and catheters of different gauges were combined to simulate varied design parameters. A syringe containing red dye was attached to the fluid delivery lumen, and the blood draw lumen was attached to a syringe hooked to a scale. This provided control of the blood draw pressure. Modulating the distance between the catheter tips allowed testing of x-distances by visually inspecting the blood draw for contamination from the red dye from the fluid delivery lumen, Figure 5. For a given trial: pressure, any contamination, and 7 mL blood draw acquisition time were recorded. Figure 9: Left – example plots generated from a clean draw; Right – example plots generated from a contaminated draw Experimental Methodology To use physical and computational models to demonstrate feasibility, optimize design and define functional limits Computational Model Figure 6 shows the results from the physical model. The matrix on the left demonstrates the parameter sets that produce uncontaminated draws (green) verse those that produce contaminated draws (red). It should be noted that with two unattached needles it can be difficult to maintain a stable spatial relationship, and this may result in false positives, as seen in two of the nodes on the left face of the matrix. The surface plot on the right shows draw times as a function of catheter gauge and draw pressure. The uncontrollable aspect of this data set is catheter length. Increased catheter length results in greater fluid drag and slower draw time. This is explains the time increase when progressing from a 21 to a 20 gauge lumen. Figure 5: Top – successful blood draw with no contamination; Bottom – contaminated blood draw Figure 6: Left – uncontaminated blood draw success (green) or failure (red) matrix; Right – 7 mL blood draw time as a function of needle gauge and draw pressure Goal – to simulate the vascular flow dynamics of the multifunction dual lumen IV catheter using finite element modeling A 2-D finite element model of the catheter was constructed in FEMLAB finite element modeling and simulation software. Figure 7 presents a mesh with appropriate types of boundary conditions. Parameters including inflow, blood draw and IV infusion velocities as well as the x-distance between lumens were altered to evaluate the design. Figure 8 relates blood velocity, blood draw rate and x-distance to the ability to gain an uncontaminated sample. If the draw rate is kept sufficiently low for a corresponding set of parameters the design accomplishes the goal. Figure 9 demonstrates both scenarios. At higher blood draw rates the sample may become contaminated with IV fluid. Inflow u = (u,v) Straight-out t · u = 0 p = 0 n · K = 0 No-slip u = 0 Figure 3: Sample mesh with appropriate boundary conditions Conclusions and Future Work The design was shown to be feasible through physical and computational models. With greater computational power the computer simulation may be extended to 3-D. Figure 10 shows a rendering of a possible final design. This includes ports on the side of the catheter for sensors allowing for continuous blood monitoring. The work towards the design and optimization of the unknown x-distance contributes to this final goal. Figure 3: Comparison of costs of current IV and blood draw system against projected multiple lumen catheter from MedTG Figure 8: Left – uncontaminated blood draw success (green) or failure (red) matrix