A microscopic view of gaseous microbubbles passing a filter screen.

Area of Science:

• Biomedical Engineering
• Fluid Dynamics
• Filtration Technology

Background:

• Gaseous microbubbles (GME) can pose risks in medical procedures.
• Effective filtration is crucial for patient safety.
• Screen filters are commonly used for GME removal.

Purpose of the Study:

• To evaluate the filtration efficacy of a specific 38-µm, 1-layer screen filter.
• To assess the filter's performance across varying flow rates.
• To analyze GME behavior during filtration using advanced imaging and Doppler techniques.

Main Methods:

• Relative filtration efficacy (RFE) was calculated using Doppler and video recordings.
• Air was introduced in 20 sequential bursts into a primed test circuit.
• Gaseous microbubbles (GME) were observed under a microscope.

Main Results:

• RFE decreased significantly with increasing flow rates (100-300 mL/min).
• Filtration was ineffective for GME smaller than 100 µm, with counts paradoxically increasing due to fragmentation.
• For GME sized 100-250 µm, RFE remained consistently above 60% regardless of flow rate.

Conclusions:

• The 38-µm, 1-layer screen filter demonstrated limited effectiveness in trapping GME.
• Filtration efficacy was particularly poor for smaller GME (<100 µm) at higher flow rates.
• GME fragmentation was observed, indicating a potential limitation of this filter type.