In vitro evaluation of gaseous microemboli handling of cardiopulmonary bypass circuits with and without integrated arterial line filters

Abstract

The delivery of gaseous microemboli (GME) by the cardiopulmonary bypass circuit should be minimized whenever possible. Innovations in components, such as the integration of arterial line filter (ALF) and ALFs with reduced priming volumes, have provided clinicians with circuit design options. However, before adopting these components clinically, their GME handling ability should be assessed. This study aims to compare the GME handling ability of different oxygenator/ALF combinations with our currently utilized combination. Five commercially available oxygenator/ALF combinations were evaluated in vitro: Terumo Capiox SX25RX and Dideco D734 (SX/D734),Terumo Capiox RX25R and AF125 (RX/AF125), Terumo FX25R (FX), Sorin Synthesis with 102 microm reservoir filter (SYN102), and Sorin Synthesis with 40 microm reservoir filter (SYN40). GME handling was studied by introducing air into the venous return at 100 mL/min for 60 seconds under two flow/ pressure combinations: 3.5 L/min, 150 mmHg and 5 L/min, 200 mmHg. Emboli were measured at three positions in the circuit using the Emboli Detection and Classification (EDAC) Quantifier and analyzed with the General Linear Model. All circuits significantly reduced GME. The SX/D734 and SYN40 circuits were most efficient in GME removal whilst the SYN102 handled embolic load (count and volume) least efficiently (p < .001). A greater number of emboli <70 microm were observed for the SYN102, FX and RX/AF125 circuits (p < .001). An increase in embolic load occurred with higher flow/pressure in all circuits (p < .001). The venous reservoir significantly influences embolic load delivered to the oxygenator (p < .001). The majority of introduced venous air was removed; however, significant variation existed in the ability of the different circuits to handle GME. Venous reservoir design influenced the overall GME handling ability. GME removal was less efficient at higher flow and pressure, and for smaller sized emboli. The clinical significance of reducing GME requires further investigation.

Figure 1.

The in vitro experimental circuit depicting the non-integrated arterial filter and oxygenator components. Emboli were measured post venous reservoir and roller pump (Transducer 1), post oxygenator (Transducer 2), and post arterial filter (Transducer 3). In circuits with integrated arterial filters, the pre-bypass filter was retained, and emboli were measured post venous reservoir and roller pump (Transducer 1), and post-oxygenator and filter at Transducer 2 and also at Transducer 3 at an equivalent distance from the arterial outlet of the oxygenator as for those with non-integrated arterial line filters.

Figure 2.

Estimated marginal means of square root transformed counts of emboli detected at Transducer 3 (after the arterial filter) at 3.5 L/min, 150 mmHg, and 5.0 L/min, 200 mmHg according to the size range of emboli. The SX/D734 and SYN40 circuits had the lowest total emboli counts, followed by the RX/AF125 and FX circuits, whilst the SYN102 had the greatest emboli counts (p < .001). Significantly less emboli were recorded above the 70–80 μm range (p < .001). (SX/D734; Capiox SX25RX oxygenator and D734 arterial filter, RX/AF125; Capiox RX25R oxygenator and AF125 arterial filter, FX; Capiox FX25R oxygenator, SYN102; Synthesis oxygenator with original venous reservoir, SYN40; Synthesis oxygenator with modified venous reservoir).

Figure 3.

The lowest emboli volume was measured at Transducer 3 in the SX/D734 and SYN40 circuits, followed by the RX/AF125 and FX, and highest in the SYN102 (p < .001). Emboli volume was increased at higher flow and pressure (p < .001). (SX/D734; Capiox SX25RX oxygenator and D734 arterial filter, RX/AF125; Capiox RX25R oxygenator and AF125 arterial filter, FX; Capiox FX25R oxygenator, SYN102; Synthesis oxygenator with original venous reservoir, SYN40; Synthesis oxygenator with modified venous reservoir).

Figure 4.

Estimated marginal means of log transformed counts of emboli detected after the venous reservoir at 3.5 L/min, 150 mmHg, and 5.0 L/min, 200 mmHg according to the size range of emboli. There was a difference in the way the venous reservoir handled the delivered embolic load (p < .001); the SYN40 reservoir had the lowest total emboli counts, followed by the FX25R, SX25, RX25R, and the SYN102. These differences were maintained over each size range. (SX; Capiox SX25RX oxygenator, RX; Capiox RX25R oxygenator, FX; Capiox FX25R oxygenator, SYN102; Synthesis oxygenator with original venous reservoir, SYN40; Synthesis oxygenator with modified venous reservoir).

Figure 5.

Total emboli volume was lower after the venous reservoir of the SYN40, followed by the FX, the SX, and RX, and the SYN102 oxygenators. Emboli volume was increased at higher flow and pressure (p < .001). (SX; Capiox SX25RX oxygenator, RX; Capiox RX25R oxygenator, FX; Capiox FX25R oxygenator, SYN102; Synthesis oxygenator with original venous reservoir, SYN40; Synthesis oxygenator with modified venous reservoir).

Figure 6.

Estimated marginal means of square root transformed counts of emboli detected post oxygenator (or post oxygenator and arterial filter in the integrated circuits) at 3.5 L/min, 150 mmHg, and 5.0 L/min, 200 mmHg according to the size range of emboli. The SYN40 had the lowest total emboli counts, followed by the SX, FX, RX, and SYN102. (SX; Capiox SX25RX oxygenator, RX; Capiox RX25R oxygenator and AF125 arterial filter, FX; Capiox FX25R oxygenator, SYN102; Synthesis oxygenator with original venous reservoir, SYN40; Synthesis oxygenator with modified venous reservoir).