T . Matsumoto et al .: J Extra Corpor Technol 2023 , 55 , 167 – 174 173
Research applications and limitations
The Hct values of the test liquids used were within the normal Hct range for cardiopulmonary bypass . In addition , the COP of the test liquids included a sufficiently wide range from the normal value of approximately 25 mmHg . As for the load on the filtration performance of the ultrafiltration membrane , the blood flow rate was 100 – 400 mL / min , and the filtration time was 4 h . Most cardiopulmonary bypass procedures are likely to be within this range . Adding a COP measurement unit to existing ultrafiltration circuits used in cardiopulmonary bypass will make it possible for many facilities to inexpensively conduct measurements during procedures . Specifically , a COP measurement circuit can be added by exposing the blood circuit and the filtration circuit to the atmosphere and arranging them in a perpendicular fashion , incorporating a switchable openair blood circuit into the blood circuit , and incorporating a switchable open-air filtration circuit into the filtration circuit .
Ultrafiltration membrane selection is important when measuring COP . As measured values are affected by the permeability of the semipermeable membrane , attention must be paid to the sieving coefficient of the membrane albumin . With an ultrafiltration membrane through which albumin passes , COP is also exerted on the filtrate , an action which is predicted to lower measurements . The effects of concentration polarization and fouling due to ultrafiltration have not been fully investigated . In addition , we have not been able to establish a method for cleaning membranes to minimize those effects .
The ends of the filtration circuit and of ultrafiltration circuits in clinical use may be connected to non-sterile containers . In our method , as the filtrate returns to the blood chamber , sterility in the filtration circuit must be maintained . We have not solved this problem with our experimental circuit . For clinical applications , it will be necessary to devise further circuits , such as a filtrate switching circuit .
COP measurement using an ultrafiltration membrane solves the problems posed by existing COP measurement methods . It is a simple , inexpensive measurement method that can be used widely in clinical practice . Although the measurement circuit requires further improvements , we expect clinical applications to emerge in the future .
In conclusion , the COP measurement with the test method using an ultrafiltration membrane revealed a strong correlation with the results of colloid osmometers currently in use , and the test method may be a useful technique for simplified COP measurement during cardiopulmonary bypass . This study was performed in vitro ; by conducting in vivo experiments , the validity of the measurements can be established . This will provide appropriate COP control values for extracorporeal circulation .
Conflict of interest The authors declare no conflict of interest .
Funding The authors received no funding to complete this research .
Data availability
The research data associated with this article are included within the article .
Ethics
This study does not involve human and / or animal subjects ; therefore , ethical approval was not required .
Author contributions
All authors contributed to the study ’ s conception and design .
Material preparation , data collection , and analysis were performed by TM , KY , and TS .
The first draft of the manuscript was written by TM and all authors commented on previous versions of the manuscript . All authors read and approved the final manuscript . Supervision : EM and TU .
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