A microscopic view of gaseous microbubbles passing a filter screen.

Purpose: The aim of this study was to investigate the filtration efficacy of a 38-mu m 1-layer screen filter based on Doppler registrations and video recordings of gaseous microbubbles (GME) observed in a microscope. Methods: The relative filtration efficacy (RFE) was calculated from 20 (n = 20) sequential bursts of air introduced into the Plasmodex (R) primed test circuit. Results: The main findings indicate that the RFE decreased (p = 0.00), with increasing flow rates (100-300 mL/min) through the filter screen. This reaction was most accentuated for GME below the size of 100 mu m, where counts of GME paradoxically increased after filtration, indicating GME fragmentation. For GME sized between 100-250 mu m, the RFE was constantly >60%, independently of the flow rate level. The video recording documenting the GME interactions with the screen filter confirmed the experimental findings. Conclusions: The 38-mu m 1-layer screen filter investigated in this experimental setup was unable to trap gaseous microbubbles effectively, especially for GME below 100 mu m in size and in conjunction with high flow rates.