Insights into Gradient and Anisotropic Pore Structures of Capiox® Gas Exchange Membranes for ECMO: Theoretically Verifying SARS-CoV-2 Permeability.

Makoto Fukuda,Kazunori Sadano,Tomohiro Mori,Asako Tokumine,Ryo Tanaka,Kiyotaka Sakai,Hitoshi Saomoto

doi:10.3390/membranes12030314

Makoto Fukuda, Kazunori Sadano + Show 5 more

Open Access

https://doi.org/10.3390/membranes12030314

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Abstract

When using the extracorporeal capillary membrane oxygenator (sample A) for ECMO treatments of COVID-19 severely ill patients, which is dominantly used in Japan and worldwide, there is a concern about the risk of SARS-CoV-2 scattering from the gas outlet port of the membrane oxygenator. Terumo has launched two types of membranes (sample A and sample B), both of which are produced by the microphase separation processes using polymethylpentene (PMP) and polypropylene (PP), respectively. However, the pore structures of these membranes and the SARS-CoV-2 permeability through the membrane wall have not been clarified. In this study, we analyzed the pore structures of these gas exchange membranes using our previous approach and verified the SARS-CoV-2 permeation through the membrane wall. Both have the unique gradient and anisotropic pore structure which gradually become denser from the inside to the outside of the membrane wall, and the inner and outer surfaces of the membrane have completely different pore structures. The pore structure of sample A is also completely different from the other membrane made by the melt-extruded stretch process. From this, the pore structure of the ECMO membrane is controlled by designing various membrane-forming processes using the appropriate materials. In sample A, water vapor permeates through the coating layer on the outer surface, but no pores that allow SARS-CoV-2 to penetrate are observed. Therefore, it is unlikely that SARS-CoV-2 permeates through the membrane wall and scatter from sample A, raising the possibility of secondary ECMO infection. These results provide new insights into the evolution of a next-generation ECMO membrane.

Highlights

Hollow fiber membrane oxygenator is used for extracorporeal membrane oxygenation (ECMO) [1–4] to treat acute respiratory distress syndrome caused by coronavirus disease (COVID-19)
It was indicated that the condensation of water vapor within the pores of the hollow fiber membrane was unlikely to be the cause of plasma leakage [6]
We focus on the durability impaired by water vapor permeation through the membrane wall and condensation in the inner lumen of the hollow fiber membrane

Summary

Introduction

Hollow fiber membrane oxygenator is used for extracorporeal membrane oxygenation (ECMO) [1–4] to treat acute respiratory distress syndrome caused by coronavirus disease (COVID-19). Extracorporeal membrane oxygenator (ECMO) is the “last stronghold” for patients with COVID-19 severe coronavirus infection [1]. Thanks to the devoted efforts of medical professionals, such as Japan ECMOnet, the weaning rate of COVID-19 critically ill patients in Japan is 67%, which is one of the highest in the world [3]. Dysfunctions of ECMO, such as the excessive pressure drop due to blood coagulation in the blood flow path [5], condensation of water vapor (wet lung) and plasma leakage [6–8], and the decrease in the gas exchange rate due to the decrease in effective membrane area have been reported. It was indicated that the condensation of water vapor within the pores of the hollow fiber membrane was unlikely to be the cause of plasma leakage [6]

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