Factors Affecting Recirculation during Veno-venous Extracorporeal Membrane Oxygenation: A Bench Study Applying Different Cannulation Techniques

Background: Veno-venous extracorporeal membrane oxygenation (vv-ECMO) offers a temporary support for patients with acute respiratory failure. However, recirculation of oxygenated blood between cannulas reduces vv-ECMO efficiency and oxygen delivery. This study investigated main variables determining recirculation in a vv-ECMO bench model applying two distinct cannulation strategies (two-site single-lumen cannulation [SLC] vs. bicaval dual-lumen cannulation [DLC])

Methods: A mock circulation loop with flow probes and pressure transducers was used to simulate a cardiovascular system in vitro. Within the loop, tubes were connected to inferior and superior vena cava and pulmonary artery of a cadaver porcine heart to mimic human right heart anatomy and valve function. A 42% water-glycerin mixture was used as blood substitute and circulated by a pulsatile centrifugal pump. A vv-ECMO circuit was inserted into the mock circulation loop. Recirculation was measured by ultrasound dilution method with different vv-ECMO setups and cannula configurations (SLC: arterial 15/17 Fr., venous 21/23; DLC [two different manufacturers]: 23 Fr. and 22 Fr.). In different series changes in recirculation were determined varying one of the following parameters: cannula position (distance, rotation), ECMO flow (ECF), cardiac output (CO), central venous pressure (CVP)

Results: With fixed other parameters, increasing CO led to a reduced recirculation, irrespective of cannulation type. In several series lower ECF corresponded well to reduced recirculation. The impact of CO and ECF was notably influenced by their ratio. When CO exceeded the selected ECF, choices of cannulas had no significant impact on recirculation. Various CVP levels did not lead to significant alterations in recirculation. When exceeding an optimal distance (> 5 cm in our model) between SLC, further retraction of the draining cannula did not change recirculation substantially. Especially rotation (one brand) and misposition had major impact on recirculation in DLC.

Conclusion: CO seems to be the primary determinant of recirculation in any cannulation scenario. Consequently, measurement of CO should be considered crucial in any patient undergoing vv-ECMO. After optimizing cannulation strategy and positioning, it becomes essential to individually fine-tune CO, ECF and address recirculation in order to maximize oxygen delivery.

Publication History

Article published online:
13 February 2024