The patency of the maxillary ostium in relation to body posture.

Eleven subjects were investigated concerning the effect of postural changes on the functional size of the maxillary ostium. The ostial size expressed as the percentage of the initial value decreased only slightly when the body position was altered from 90 degrees (sitting) to 30 degrees, while the decrease between 30 degrees and 0 degrees (lying) was more pronounced. A cuff around the neck inflated to 25 mmHg gave a decrease corresponding to a value of 20 degrees body position. Insufficient ventilation of the paranasal sinuses when lying down may result, especially in cases already having small ostia in the sitting position.