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Design Innovation

Assessment of Current Continuous Hemofiltration Systems and Development of a Novel Accurate Fluid Management System for Use in Extracorporeal Membrane Oxygenation

[+] Author and Article Information
Philippe Sucosky

Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Parker H. Petit Biotechnology Building, 315 Ferst Drive, Atlanta, GA 30332-0363philippe.sucosky@bme.gatech.edu

Lakshmi P. Dasi

Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Parker H. Petit Biotechnology Building, 315 Ferst Drive, Atlanta, GA 30332-0363ld67@mail.gatech.edu

Matthew L. Paden

Division of Pediatric Critical Care, Children’s Healthcare of Atlanta at Egleston, Emory University School of Medicine, 1405 Clifton Road, NE, Atlanta, GA 30322matthew.paden@choa.org

James D. Fortenberry

Division of Pediatric Critical Care, Children’s Healthcare of Atlanta at Egleston, Emory University School of Medicine, 1405 Clifton Road, NE, Atlanta, GA 30322james.fortenberry@choa.org

Ajit P. Yoganathan

Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, U.A. Whitaker Building, 313 Ferst Drive, Room 2119, Atlanta, GA 30332-0535ajit.yoganathan@bme.gatech.edu

J. Med. Devices 2(3), 035002 (Aug 07, 2008) (8 pages) doi:10.1115/1.2952818 History: Received September 13, 2007; Revised May 15, 2008; Published August 07, 2008

Extracorporeal membrane oxygenation (ECMO) with a renal replacement therapy such as continuous venovenous hemofiltration (CVVH) provides life-saving temporary heart and lung, and renal support in pediatric and neonatal intensive care units. However, studies have shown that this approach may be hampered due to the potentially inaccurate fluid delivery∕drainage of current intravenous (IV) fluid pumps, creating potential for excessive fluid removal and undesired degrees of dehydration. We present a simple and novel accurate fluid management system capable of working against the high volume flow and pressures typically seen in patients on ECMO. The accuracy of the in-line system implemented at Children’s Healthcare of Atlanta at Egleston was assessed experimentally. The data assisted in the development of a novel automated and accurate fluid management system that functions based on a conservation of volume approach to limit the inaccuracies observed in typical clinical implementations of CVVH. IV pump accuracy measurements demonstrated a standard error in net ultrafiltrate volume removed from the patient of up to 848.5±156ml over a period of 24h, supporting previous observations of patient’s dehydration during the course of a combined ECMO-CVVH treatment and justifying the need for a new fluid management system. The innovative design of the new device is expected to achieve either a perfect or controlled negative fluid balance between the ultrafiltrate and replacement fluid flow rates. Perfect fluid balance is achieved by imposing an identical displacement on two pistons, one delivering replacement fluid to the circuit and the other draining ultrafiltrate from the hemofilter. Fluid removal is managed via a second syringe-pump system that reduces the net replacement fluid flow rate with respect to the ultrafiltration flow rate. The novel fluid management system described in this paper is expected to provide an effective method to control precisely fluid flow rates in patients on ECMO. Therefore, this device could potentially improve the efficacy of ECMO therapy and constitute a safe and effective way of reducing fluid overload in patients with cardiorespiratory failure.

FIGURES IN THIS ARTICLE
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Copyright © 2008 by American Society of Mechanical Engineers
Topics: Fluids , Pumps , Membranes
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Figures

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Figure 1

Schematic of a typical combined ECMO-CVVH system

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Figure 2

Schematic of the setup used to measure the IV pump accuracy. The system that consists of a source tank fed continuously with fluid via a centrifugal pump and maintaining a constant pressure head by discharging fluid in an overflow sink.

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Figure 3

Results of the IV pump accuracy measurements. The flow rate error, calculated as the difference between the programmed and actual flow rate delivered by the pump for three different flow rates, is plotted as a function of the pressure differential applied across the IV pump.

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Figure 4

Principles of the novel fluid management system based on conservation of volume approach: (a) Step 1: ultrafiltrate drainage and fluid replacement delivery; (b) Step 2: replacement fluid chamber refill and ultrafiltrate chamber drainage into storage bag. A syringe pump located downstream of the replacement fluid chamber is used to achieve a net negative fluid balance by reducing the delivery of replacement fluid.

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Figure 5

CAD rendering of the system achieving perfect fluid balance

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Figure 6

CAD rendering of the new accurate CVVH system: (a) front panel; (b) rear panel.

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Figure 7

Details of the front panel of the new CVVH system

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Figure 8

Mechanisms involved in the production of a perfect fluid balance: (a) Step 1: replacement fluid delivery and ultrafiltrate removal; (b) Step 2: replacement fluid syringe refill and ultrafiltrate syringe drainage.

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Figure 9

Additional mechanisms involved in the production of a negative fluid balance: (a) Step 1: replacement fluid extraction; (b) Step 2: negative fluid balance syringe drainage.

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