Including auditory tube function on models is relevant to assess water exposure after tympanostomy tubes–Multiphase computerized fluid dynamics model

Introduction: Myringotomy with tympanostomy tube is the most common otologic surgery and some patients are still advised to avoid water. However, there is no evidence supporting this, with published papers questioning the need for this advice. Methods: A Multiphase Computational Fluid Dynamics (CFD) model was created using computerized tomography images of a child's healthy ear. It was then used to study the flow of fluids through the external ear, tympanic cavity, and auditory tube, with and without submersion. Results: The model accurately described the behavior of the air retained in the patient's nasopharynx and tympanic cavity. A simulated elevation of pressure in the external auditory canal without submersion, without increase of pressure in the nasopharynx, demonstrated that fluids promptly crossed the tympanostomy tube into the middle ear. However, simulated elevation of pressure in the external auditory canal with concurrent elevation of air pressure in the nasopharynx during submersion did not lead to passive tube opening nor to any detectable flow through the tympanostomy tube. Conclusions: In the model, submersion increases pressure in the nasopharynx which offsets the pressure in the external auditory canal. So, in the absence of a pressure gradient, no passive tubal opening took place, and no air or fluid flow was detected through the transtympanic tube. This model now includes the exhaust function of the auditory tube in the model and shows its relevance.