The Liebau phenomenon: a translational approach to new paradigms of CSF circulation and related flow disturbances.

PURPOSE: The aim of the study is to provide a comparison between Liebau's effect, underlying the working principles of impedance pumps, and the cerebrospinal fluid (CSF) circulation.

METHODS: Gerhard Liebau was a cardiologist with a specific interest in severe aortic regurgitation. Such interest drew his scientific attention to the flow-driven efficiency of valveless pumps. During one of his experiments, he assembled two rubber tubes of different sizes and documented how water could be aspirated against gravity when the tube of larger diameter underwent rhythmic compression. He subsequently tested an elastic tube connected to glass pipes of the same size on both ends, immersed in a water bucket. When the elastic tube was periodically pumped with a finger, a net flow could be observed in both directions; depending on the pumping site on the elastic tube, the flow was directed towards the most closely connected glass tube. The principles of a hydraulic system of different elasticity and compliance were also recently applied to the physiology and fluid dynamics of embryonic hearts.

RESULTS: Impedance pumps and the CSF dynamics model are both valveless systems and can both be activated by the effects of the cardiac cycle. The novel hydraulic model of impedance pumps was the foundation for the development of modern valveless micropumps and contributes to explain how the embryonic valveless tubular heart is capable of generating blood flow.

CONCLUSIONS: Liebau's effect and the mechanism of impedance pumps can enlighten some of the aspects of CSF dynamics and related flow disturbances.