Patency of the maxillary sinus ostium in healthy individuals

In a group of 20 healthy subjects the patency of the maxillary ostium has been evaluated in 35 maxillary sinuses with three different techniques: simultaneous pressure recording in the sinus and the ipsi- and contralateral nasal cavity; simultaneous recording of differential pressure between the sinus and the ipsilateral nasal cavity and air-flow through the ostium during nasal breathing; recording of the pressure rise in the sinus with an artificial air-flow of 1 litre per minute applied to the sinus. The tests were carried out in sitting and recumbent positions. In 5 persons (10 sinuses) a retest was performed after 2 months. These subjects were also tested with an inflatable neck cuff in order to obtain an increased venous pressure. Rhinomanometry at rest and after physical effort was also performed. The pressure relationship between the maxillary sinus and the ipsilateral nasal cavity was 1:1 in both the sitting and the recumbent position, but less than 1 when the contralateral nasal cavity was measured. Pressure recording alone gives no quantitative information about the patency of the ostium. Determination of the ostial resistance during nasal breathing could be performed in 13 sinuses, but in the remaining 22 the ostia were too wide to give a measurable resistance. The equivalent ostial diameter during inspiration could be estimated in 12 of the sinuses from a diagram constructed from known ostial diameters in model experiments. With an artificial air-flow applied into the sinus, the equivalent ostial diameters could be estimated from the diagram in all cases. No statistical difference was found in comparable cases between the mean equivalent ostial diameters estimated with the two methods. The equivalent ostial diameters showed a statistically significant reduction in the recumbent position and after application of the neck cuff. A statistically significant relationship was also found between the airway resistance of the nasal cavity and the equivalent diameter of the ostium in sitting and recumbent positions. Such a relationship could not be found between the equivalent ostial diameters measured at rest and the nasal resistance recorded after physical effort.