Flow field dynamics in the pumping function of eustachian tube under varied middle ear pressure states

The Eustachian tube, a conduit linking the tympanic cavity to the nasopharynx, poses challenges for observation of its pressure dynamics due to its concealed anatomical position. Furthermore, computational models have not yet accurately replicated its intricate structure. We propose that simplification of the Eustachian tube's structure may represent a crucial step toward elucidating the mechanisms underlying intraluminal pressure variation. In the present study, simplified models were constructed from CT scans of patients with patulous Eustachian tube. These models captured the tube's key morphological features, including a blind-ended tubular structure with a sealed tympanic orifice, an open pharyngeal orifice, and a deformable central segment. Particle image velocimetry (PIV) was used to enable visualization of flow field alterations within the lumen during the transition from a closed to an open state under various simulated middle ear pressure conditions. The following phenomena were observed: (1) Bidirectional pumping at the onset of intraluminal negative pressure, characterized by simultaneous suction from both sides toward the center; (2) Variation of the pumping phenomenon under different middle ear pressure conditions; (3) Vortex generation at the tympanic orifice upon tubal opening under middle ear negative pressure. These findings provide novel insights into the functional mechanics of the Eustachian tube, and offer supporting evidence for the surgical rationale of myringotomy with grommet insertion in patients with otitis media with effusion (OME).