Investigation of flow characteristics in the maxillary sinus where polypoid changes develop

The results showed that the epithelial surfaces where polypoid changes occur are located in the lower part of the maxillary sinus which contains a protruding zone of the sinus and are characterized by stagnation of air during the entire respiration period. Due to the geometric characteristics, a very slow recirculating motion was found to occur in the bulging area for approximately half of the respiration period as a result of interaction with a larger-scale, counter-rotating vortex filling the middle of the maxillary sinus. With a much smaller velocity inside the maxillary sinus compared to that typically found in the airway passage through the middle meatus, both wall shear and pressure changes were found to be vanishingly small along the epithelial surface of the maxillary sinus where polypoid changes were found.