To Purge or Not to Purge

Area of Science:

• Cardiovascular Surgery
• Biomedical Engineering
• Medical Device Technology

Background:

• Manufacturers sometimes recommend purging oxygenators with integrated arterial filters to remove gaseous microemboli (GME).
• The efficacy of this purging procedure in enhancing GME removal during cardiopulmonary bypass remains unclear.
• Evaluating this safety feature is crucial for optimizing extracorporeal circulation procedures.

Purpose of the Study:

• To investigate the efficiency of purging oxygenators with integrated arterial filters in reducing GME.
• To compare GME removal rates with the purge line open versus closed under continuous GME challenge.
• To assess the impact of purging on filter performance across different oxygenator types.

Main Methods:

• An in vitro study utilizing five types of contemporary oxygenators with integrated arterial filters (progressive, cascade, screen, and self-venting filtration).
• Testing was conducted using porcine blood at flow rates of 3 and 5 L/min, with a continuous GME load of 1,000 mL air/min.
• Filter efficiency was calculated by comparing GME counts pre- and post-oxygenator using a bubble counter, with and without purging.

Main Results:

• No statistically significant difference in filter efficiency was observed between purged and non-purged groups for most oxygenators.
• At 3 L/min, average filter efficiency remained largely unchanged, with the largest difference being 0.9%.
• At 5 L/min, purging showed a decrease in efficiency for one screen filter (55.7% vs. 42.4%) and minor reductions in others, indicating no benefit.

Conclusions:

• Purging oxygenators with integrated arterial filters does not enhance their efficiency in removing gaseous microemboli under continuous challenge.
• The tested filter designs demonstrated consistent GME removal performance irrespective of the purge line status.
• Current evidence suggests that purging may not be a necessary additional safety feature for GME reduction with these devices.