Development of a New Arterial-Line Filter Design Using Computational Fluid Dynamics Analysis

Abstract

Arterial-line filters used during extracorporeal circulation continue to rely on the physical properties of a wetted micropore and reductions in blood flow velocity to affect air separation from the circulating blood volume. Although problems associated with air embolism during cardiac surgery persist, a number of investigators have concluded that further improvements in filtration are needed to enhance air removal during cardiopulmonary bypass procedures. This article reviews theoretical principles of micropore filter technology and outlines the development of a new arterial-line filter concept using computational fluid dynamics analysis. Manufacturer-supplied data of a micropore screen and experimental results taken from an ex vivo test circuit were used to define the inputs needed for numerical modeling of a new filter design. Flow patterns, pressure distributions, and velocity profiles predicted with computational fluid dynamics softwarewere used to inform decisions on model refinements and how to achieve initial design goals of ≤225 mL prime volume and ≤500 cm2 of screen surface area. Predictions for optimal model geometry included a screen angle of 56° from the horizontal plane with a total surface area of 293.9 cm2 and a priming volume of 192.4 mL. This article describes in brief the developmental process used to advance a new filter design and supports the value of numerical modeling in this undertaking.

Sequential Blood Filtration for Extracorporeal Circulation: Initial Results from a Proof-of-Concept Prototype

“…Table 2 details the outcomes for pressure loss performance testing, showing a range in pressure drop between 26 and 33 mmHg at 6 L/min. Prototype performance was better than expected, demonstrating a flow-through resistance less than the value predicted in phase one of the research (13). Table 3 summarizes the grand means and SDs for bubble number and volume measured prefilter.…”

“…As illustrated, the prototype improves on flow through the filter by straightening the blood path and eliminating any sharp angles. Additionally, unlike the Quart in which flow through each of its filter cassettes is directed down along a guide plate toward the filter outlet ( 16), the prototype is designed to improve lift in the fluid entering the filter to help augment microbubble separation from the blood supply returning to the patient (13). As flow across the filter screens in the Quart moves downward, a rising inner wall in the prototype is positioned between the inlet and outlet so that flow across its filter screens is directed upward (13).…”

“…However, in considering the amount of regulatory control over the manufacturing process and performance of medical devices, it was felt that large imperfections in the handmade model would make any small performance variations that may exist within each commercial filter type acceptable for this proof-of-concept study. Lastly, although the rationale for using a whole blood or blood analog for studies concerned with creating near clinical conditions is clear (3,(16)(17)(18), the use of a nonblood analog in this work was required to confirm phase one predictions of the research and maintain the development link between the numerical model and physical prototype (13). Although the priming solution used reduces viscous drag forces and the amount of free gas pulled across each test filter, the results remain comparable and allow the commercial filters to serve as a suitable benchmark to compare the prototype with.…”

“…Efforts to establish performance of the new design were carried out in two phases. After phase one, which included numerical modeling and analysis using computer-based software (13), prototype manufacturing and testing were completed in phase two. This article details the outcomes of phase two research used to analyze and evaluate a new concept in micropore filtration for ECC and compares a prototype of the new design with four commercially available arterialline filters.…”