Pressure measurements in the normal and occluded rabbit maxillary sinus

Occlusion of the maxillary ostium is considered to be a key factor in the pathogenesis of maxillary sinusitis. In this study, the authors determined the effect of ostial occlusion on pressure in the rabbit maxillary sinus which, like most humans, has only one ostium. We compared pressures in the normal and occluded maxillary sinus and the nasal cavity during spontaneous breathing in anesthetized adult animals. Serial pressure measurements were obtained from sinuses with patent ostia in nasal-breathing rabbits and with occluded ostia in both nasal-breathing and tracheotomized animals. Sinuses with patent ostia showed pressure curves synchronous with the respiratory cycle. Inspiratory and expiratory pressures in the nasal cavity and the sinus were isobaric. Sinuses with occluded ostia initially developed a positive pressure followed by a negative pressure that reached a subatmospher-ic plateau of-28.2 ± 7.3 mm H₂0 (mean ± standard deviation [SD]) within 20 to 50 minutes. This is the first quantitative study of sinus pressures using the rabbit as an animal model. The findings may contribute to a better understanding of the role of ostial occlusion in the pathogenesis of maxillary sinusitis in humans.