T. Rath et al.: J Extra Corpor Technol 2026, 58, 19 – 31 27
Figure 6. Average GME count and size data. Average( A) venous and( B) arterial GME count and size for all 25 trials, reservoir types( Medtronic Affinity Fusion, LivaNova SORIN Inspire 8F, and Terumo CAPIOX FX25), levels( 200 mL, 500 mL, and 1000 mL) and suction flow rates( 25 RPM( 0.32 L / min), 50 RPM( 0.65 L / min), 75 RPM( 0.99 L / min) and 100 RPM( 1.32 L / min)).
differences in the average bubble counts between changes in sucker flow were much less compared with those from the venous sensor. Significant changes in bubble count were observed as the suction speed increased from 25 to 100 RPM and from 50 to 100 RPM, indicating that at these higher suction flows, bubbles can still escape from the oxygenator and enter the patient. No significant interaction was found between level and suction speed using the arterial sensor data, as observed with the venous sensor. Additionally, the reservoir level did not appear to influence the amount of arterial air detected.
The size of the GME, detected in micrometers, was averaged across all our runs and is displayed in Figure 6. The venous( post-reservoir) sensor captured a wide range of bubble sizes, with most falling between 30 and 80 microns, with some significant outliers. The arterial sensor’ s distribution appeared similar, but it was interesting that many bubbles, less than 40 microns in diameter, were observed. The arterial filter pore size of the oxygenators tested ranged from 25 to 38 microns, which may explain why many bubbles detected were less than 40 microns.
Mechanism This study did not directly investigate the mechanism causing the observed increase in bubble transmission with increased suction speed and changes in reservoir level. Interfacial bubbles( bubbles on a liquid) tend to fractionate, creating numerous smaller“ daughter” bubbles rather than disappearing [ 40 ]. In this study, fractionation or bubble rupture might depend on how quickly the aerated blood shuttles into the reservoir( suction speed), causing bubble rupture. Once these larger bubbles rupture, the distance they travel to the reservoir exit( reservoir level) plays a role. The mechanism describing their movement is multifactorial and can relate to blood viscosity, blood components that can carry the micro-air through the circuit, and the design of the reservoir, particularly at air-blood mixing surfaces.
Blood viscosity may affect this transmission. Mitchell et al. demonstrated that blood viscosity is directly proportional to GME generation and transmission [ 26 ]. We used bovine blood hematocrit as a proxy for viscosity, which was kept constant in this study, but we did not directly measure blood viscosity. In clinical settings, viscosity continuously fluctuates due to blood transfusions or fluids administered during surgery [ 35 ]. While these changes are typically minor, they may still affect the amount of GME transmitted.
In addition to blood viscosity, blood composition plays a role in GME transmission. Preliminary trials conducted before the commencement of our work revealed that circuits containing crystalloids yielded minimal GME creation and