Geometry, shunt, and recirculation in hollow-fiber oxygenators

In extracorporeal circulation, hollow-fiber oxygenators are usually evaluated by gas transfer, pressure drop, and priming volume, but shunt and recirculation also critically affect performance.Shunt refers to blood bypassing effective fiber contact, while recirculation involves internal looping within the device, both altering oxygen transfer, hemocompatibility, and embolic safety.Geometry strongly influences these dynamics: cylindrical, plate-type, spiral, and radial designs each present benefits and risks of preferential channels, stagnation, or internal loops.Monitoring inlet and outlet flows provides a simple way to estimate shunt fraction, with values above 5-10% indicating clinically relevant losses.Pump technology further modulates these effects, as roller pumps deliver fixed flow while centrifugal pumps introduce preload-and afterload-dependent variability.Drawing a parallel to physiological shunts, quantifying these hidden flows may improve oxygenator assessment and perfusion safety, linking device design, pump type, and monitoring to more effective extracorporeal support.