EXPERIMENTAL STUDIES OF THE RESOLUTION OF ACOUSTIC RHINOMETRY IN-VIVO

The ability of acoustic rhinometry to detect objects of defined size i n nasal cavities has hitherto been investigated only in cadavers and m odels. We aimed to determine the resolution of the technique in the no se of living subjects. Silicone spheres of 3.0, 5.0, and 7.0 mm diamet er were placed at two sites in the decongested and locally anaesthetis ed nasal cavities of 3 healthy adults. Acoustic rhinometry area-distan ce functions were obtained before and after insertion of the spheres, with further control data obtained after removal of the sphere from th e nasal cavity. Six nasal cavities were studied in each test state on two separate occasions. The 3.0 mm sphere caused a statistically signi ficant change in cavity volumes in only 17% of cases when placed in th e middle meatus and in 8% at,the nasal value (Mann-Whitney U-test; p < 0.05). The detection rates for the 5.0 mm sphere were 50% in the midd le meatus and 50% at the nasal valve. When the control and test curves were compared by superimposition and the cross-sectional areas at the site of perturbations compared statistically (Mann-Whitney U-test) th e detection rates in the middle meatus were: 33%-3.0 mm and 67%-5.0 mm sphere. The detection rate at the nasal valve region was 25%-3.0 mm s phere and 58%-5.0 mm. The 7.0 mm sphere was detected in 100% cases by volume changes, and 80% by area changes. Acoustic rhinometry can relia bly detect changes of volume and area in the living nose resulting fro m the introduction or a 7 mm sphere into the nasal valve or middle mea tal region in most cases. Smaller spheres are detected in only a fract ion of cases. The resolution of the technique is therefore close to 7. 0 mm (1.44 cm(3)). These findings are important when interpreting acou stic rhinometry data in monitoring patients with nasal pathology.