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An in vitro comparison of the ability of three commonly used pediatric cardiopulmonary bypass circuits to filter gaseous microemboli

We have read with great interest the article entitled, “An in vitro comparison of the ability of three commonly used pediatric cardiopulmonary bypass circuits to filter gaseous microemboli”, which has been published in Perfusion. We are pleased to see that more investigators are doing evidence-based research to compare components of the pediatric cardiopulmonary bypass (CPB) circuitry and would like to share our experiences with a similar design for this important topic. In their study, the authors compared three pediatric CPB circuits in terms of gaseous microemboli filtration: the Terumo BabyRX05 oxygenator with a Terumo Capiox AF02 arterial filter; the Terumo BabyFX05 oxygenator with an integrated arterial filter, and the Sorin KID D100 oxygenator with the Sorin KIDS D 130 arterial filter. During the experiments, the purge line was kept open in each circuit and the arterial line pressure was maintained at approximately 125-150mmHg. One of the major factors impacting gaseous microemboli capture in a cardiopulmonary bypass (CPB) circuit is the flow rate, together with the circuit pressure and the temperature. We have documented, in our previous studies, that an open purge line connected to a separate arterial filter would have significant impact on the flow rate at the post-arterial filter site due to the shunting (stolen) blood flow, especially under high arterial line pressures, whereas the shunting flow of a purge line with an integrated arterial filter could be very minimal. Therefore, the flow rates at the postarterial filter site could be quite different in these three circuits. For the Terumo FX05 oxygenator with an integrated arterial filter, the purge line could only start from a POST-arterial filter port, which is totally different from the other two circuits which use separate arterial filters. These limitations may have influenced significantly the results of this study. Additionally, we have documented that the reservoir also plays an important role in gaseous microemboli capturing in a CPB circuit as the authors also discussed in their article. As there is no flow probe after the arterial filter shown in the schematic of the circuit (Figure 1), the absolute flow rate delivered to the patient can vary for each oxygenator. Additionally, the diameter of the purge line can greatly affect the total flow delivered to the patient. Therefore, we suggest that, in future experiments, a flow probe should be placed after the arterial filter to match the flow delivered to the patient with the percentage of rated flow. We would also suggest that authors might use lower flow rates (such as 300 ml/min to 500 ml/min) and temperatures in future studies, particularly for the neonatal design of the Sorin KID D100 oxygenator. We are also pleased to see that authors placed the second oxygenator after the arterial filter to capture most of the emboli and repeated the following injection after a very short interval, which we will adapt for our future experiments. Once again, it was a pleasure to see that more translational research has been done for scientific evaluations of pediatric oxygenators.