A Membrane Lung Design Based on Circular Blood Flow Paths

Abstract

Current hollow fiber membrane lungs feature a predominantly straight blood path length across the fiber bundle, resulting in limited oxygen transfer efficiency due to the diffusion boundary layer effect. Using computational fluid dynamics and optical flow visualization methods, a hollow fiber membrane lung was designed comprising unique concentric circular blood flow paths connected by gates. The prototype lung, comprising a fiber surface area of 0.28 m2, has a rated flow of 2 L/min and the oxygenation efficiency is 357 mL/min/m2. The CO2 clearance of the lung is 200 mL/min at the rated blood flow. Given its high gas transfer efficiency, as well as its compact size, low priming volume, and propensity for minimal thrombogenicity, this lung design has the potential to be used in a range of acute and chronic respiratory support applications, including providing total respiratory support for infants and small children and CO2 clearance in adults.

Technical Advances in the Field of ECMO

“…Computational flow dynamics and in vivo testing of this low-resistance device demonstrated that the mixing of blood as it traversed the gated compartments augmented O 2 transfer and sufficiently removed CO 2 at a rated flow of 2 L/min. 46 The compliant thoracic artificial lung consists of a flexible chamber containing a mat of hollow-fiber bundles through which blood is routed by means of inlet and outlet conduits, while fresh gas flows adjacently. 47 Initial animal experiments with this device showed that the load on the right ventricle could be reduced with the device positioned between the pulmonary artery and left atrium, and flows Ͼ 7 L/min could be achieved.…”

Low-Resistance, Concentric-Gated Pediatric Artificial Lung for End-Stage Lung Failure

“…Data from our previous work were used to provide the necessary resistance data to simulate the fiber bundle as an isotropic porous media. 26 The experimental resistance data for the original fiber mat (17 fibers/cm) were scaled down linearly by multiplying by a factor κ κ LR , where κ LR is the predicted permeability of the low-resistance fiber mat (six fibers/cm) into equation 1. This provided the resistance data for the low-resistance fiber mat to be input into the porous media model for the CFD simulations.…”

“…The required gas exchange SA for the current device was estimated by scaling our previous design, which had a SA = 0.28 m 2 and a rated flow of 2 L/min, but a pressure drop of approximately 100 mm Hg. 26 Scaling down SA linearly (assuming equivalent gas exchange efficiency in the previous and new designs) gave a basis SA of 0.1 m 2 for the new design because this SA is expected to provide the necessary gas exchange to satisfy the rated flow requirement. Blood flow was simulated using the Solidworks Flow Simulation add-in (Dassault Systémes), and velocity and pressure profiles were generated (Figure 2).…”

“…At 0.75 L/min, pressure drop in a single-inlet MLung using a fiber mat with 17 fibers/cm and a fiber length of 2 cm was 38 mm Hg (from previous work). 26 To further reduce pressure drop, three changes were made from the previously published design (Table 1): 1) the use of a dual-inlet design; 2) fiber length increased to 3 cm; and 3) reduction of the fiber bundle porosity by using a low-density fiber mat (six fibers/cm). Each of these changes independently reduces pressure drop, and when the fiber bundle is modeled as an isotropic porous media, a pressure drop of 2 mm Hg is predicted at a flow rate of 0.75 L/min.…”

“…[21][22][23][24][25] Recently, we demonstrated a membrane lung based on a series of concentric gates, resulting in a circular blood flow path that induces secondary flows, disrupting the boundary layer, and improving overall gas exchange. 26 Based on our previous work, this study aims for designing a new AL that provides adequate gas exchange and pressure drop for pediatric patients.…”