An In Vitro Method to Quantitate Gaseous Microemboli Production of Bubble Oxygenators

Abstract

An in vitro method to collect and quantify volumes of gaseous microemboli generated by a bubble oxygenator has been developed. Gaseous microemboli generated by a bubble oxygenator are captured and collected in a vortex separation test cell. The cells are pressurized and the resultant pressure changes are converted to volume gas readings using a standard calibration curve. A doppler type ultrasonic detector and this new technique were compared in order to determine correlation between the two techniques. Results of this study indicate that the ultrasonic detector “counts” do not quantitatively relate to volume of air captured in the test cells. The placement of the ultrasonic detector within the circuit can alter its readings, e.g., proximity to turbulent areas caused by connectors or positive/negative pressure excursions due to the blood pump. Significant differences were noted when fresh, bovine blood with physiologically balanced gases were substituted for lactated Ringer's solution and 100% oxygen due to differences in bubble stability and saturation levels. Based on these findings, the use of vortex collection cells can provide a more accurate profile of gaseous microemboli production by various cardiopulmonary devices. A circuit and procedure are described for this purpose.