Microbubble generation and transmission of medtronic's affinity hardshell venous reservoir and collapsible venous reservoir bag: an in-vitro comparison

Abstract

Microemboli are implicated in neurological injury; therefore, the extracorporeal circuit (ECC) should not generate microbubbles or transmit introduced air. The venous reservoir is the first component in the ECC designed to remove introduced air. The purpose of this study was to investigate the relative safety of two kinds of adult venous reservoirs--the closed soft-shell venous reservoir (SSVR [Medtronic CBMVR 1600]) and the open hard-shell venous reservoir (HSVR [Affinity NT CVR])--in terms of microbubble generation and introduced air transmission. A recirculating in-vitro circuit was used to compare the two reservoirs with the SSVR further assessed in a fully closed or partially open state. Microbubbles were counted using a Hatteland CMD-10 Doppler in the outflow of the reservoirs before (microbubble generation) and after infusing 20 mL/min of air into the venous line (microbubble transmission) while altering pump flow rates (3 L/min; 5 L/min) and reservoir prime (200 mL; 700 mL). Negligible bubble generation was noted in the SSVRs at both flow rates and either reservoir volume. However, microbubble generation was significant in the HSVR at the higher flow rate of 5 L/min and lower reservoir volume of 200 mL. When infusing air, a flow of 3 L/min was associated with insignificant to small increases in microbubble transmission for all reservoirs. Conversely, infusing air while flowing at 5 L/min was associated with significantly more microbubble transmission for all reservoirs at both low and high reservoir volumes.The SSVR is as safe as the HSVR in microbubble handling as the generation and transmission of microbubbles by the SSVR is not more than the HSVR over a range of prime volumes and flow rates. As both reservoirs transmitted microbubbles at higher pump flow rates regardless of reservoir volumes, it is important to eliminate venous air entrainment during cardiopulmonary bypass.

Figure 1.

In-vitro circuit. See text for details. Note: not to scale.

Figure 2.

Boxplots of microbubble generation (counts/min) in the outflow of the three venous reservoir types at pump flows of 3 L/min or 5 L/min and reservoir volumes of 200 mL or 700 mL.

Figure 3.

Boxplots of microbubble transmission (counts/min) in the outflow of the three venous reservoir types during venous line air infusion at 20 mL/min at pump flows of 3 L/min or 5 L/min and reservoir volumes of 200 mL or 700 mL.