Background and Objectives: This study aimed to investigate the risk and mechanisms of air entry into the extracorporeal membrane oxygenation (ECMO) circuit through the central venous catheter (CVC) in a veno-venous configuration. The primary goal was to assess the impact of different air volumes on ECMO circuit performance at varying pump speeds. Material and Methods: The study utilized a circuit model to simulate ECMO conditions and evaluate the potential entry points of air, specifically through the unprotected lumen of the CVC. Various interventions, such as the use of a closed three-way stopcock or clave, were implemented to assess their efficacy in preventing air entry. Results: The unprotected lumen of the central venous catheter posed a significant risk for air entry into the ECMO circuit. The introduction of a closed three-way stopcock or clave proved effective in preventing air ingress through the central venous catheter. Auditory cues, such as a distinct hissing sound, served as an early warning sign of air presence in the circuit. The study demonstrated that even small volumes of air, as minimal as 1 mL, could pass through the oxygenator at specific pump speeds, and larger volumes could lead to pump dysfunction. Conclusions: The study identified the unprotected lumen of the central venous catheter as a potential entry point for air into the ECMO circuit. The use of a closed three-way stopcock or one-way valve was found to be a reliable protective measure against air infiltration. Early detection through the observation of a hissing sound in the circuit provided a valuable warning sign. These findings contribute to enhancing the safety and performance of ECMO systems by minimizing the risk of air embolism.

2nd Department of Medicine Department of Cardiovascular Medicine 1st Faculty of Medicine Charles University Prague and General University Hospital 10000 Prague Czech Republic

Center for Intensive Internal Medicine University Medical Center Zaloska 7 1000 Ljubljana Slovenia

Department of Advance Biomedical Sciences Federico 2 University Via Pansini 5 80131 Naples Italy

Department of Cardiovascular Surgery University Medical Center Zaloska 7 1000 Ljubljana Slovenia

Emergency Center General Hospital Celje Oblakova 5 3000 Celje Slovenia

Faculty of Medicine University of Ljubljana Vrazov trg 2 1000 Ljubljana Slovenia

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