Abstract
This work investigates the plasma skimming effect in a spiral groove bearing within a hydrodynamically levitated centrifugal blood pump when working with human blood having a hematocrit value from 0 to 40%. The present study assessed the evaluation based on a method that clarified the limitations associated with such assessments. Human blood was circulated in a closed-loop circuit via a pump operating at 4000 rpm at a flow rate of 5 L/min. Red blood cells flowing through a ridge area of the bearing were directly observed using a high-speed microscope. The hematocrit value in the ridge area was calculated using the mean corpuscular volume, the bearing gap, the cross-sectional area of a red blood cell, and the occupancy of red blood cells. The latter value was obtained from photographic images by dividing the number of pixels showing red blood cells in the evaluation area by the total number of pixels in this area. The plasma skimming efficiency was calculated as the extent to which the hematocrit of the working blood was reduced in the ridge area. For the hematocrit in the circuit from 0 to 40%, the plasma skimming efficiency was approximately 90%, meaning that the hematocrit in the ridge area became 10% as compared to that in the circuit. For a hematocrit of 20% and over, red blood cells almost completely occupied the ridge. Thus, a valid assessment of plasma skimming was only possible when the hematocrit was less than 20%.
Highlights
Understanding the blood flow dynamics in mechanical circulatory support devices is important for the development of more hemocompatible devices, with the aim of preventing thrombosis and hemolysis
The developed system and the experimental method based on the optical theory of blood demonstrated indicate that the plasma skimming (PS) effect does occur in the spiral groove bearing (SGB) of a centrifugal blood pump
The present results show that PS appeared at the PS efficiency (PSE) was approximately 90% in over the HCTW range from 0 to 20%
Summary
Understanding the blood flow dynamics in mechanical circulatory support devices is important for the development of more hemocompatible devices, with the aim of preventing thrombosis and hemolysis. Many researchers have investigated and simulated such dynamics using computational fluid dynamics (CFD) and particle image velocimetry [1,2,3,4,5]. These conventional studies have assessed blood flow solely on the macroscopic level. It would be helpful to have a better understanding of blood flow dynamics on the scale of individual cells at such hydrodynamic bearing regions, to assist in the development of novel hemocompatible devices
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