Extracorporeal membrane oxygenation (ECMO) and extracorporeal carbon dioxide removal (ECCO₂R) provide respiratory support aimed at gaining time to allow patient’s recovery from hypoxemic and/or hypercapnic respiratory failure, respectively.¹ However, in recent years, very few new oxygenators have been developed.^2–4 In this report, we describe a newly designed oxygenator, a component of the MOBYBOX (Hemovent, Aachen, Germany). This oxygenator has a membrane lung surface area of 1.6 m² consisting of typical polymethylpentene fibers. The fibers are arranged in a stacked design with perpendicular blood flow in theory characterized by a low-pressure difference across the oxygenator. The corners of the oxygenator have been sealed, and the blood flow is directed in a helical fashion into the fiber bundle to eliminate stagnant regions and optimize washout. Limited stagnation was achieved by means of computational flow dynamics (CFD) in silico. Recent long-term sheep experiments revealed a high carbon dioxide (CO₂) removal capacity.⁵ The aim of the current animal study was to evaluate the pressure gradient across the oxygenator and the gas exchange performance within a blood flow rate (BFR) range of 1–4 L/min, typically used in clinical practice for ECMO and ECCO₂R.