[A fundamental study of relationships between rhinomanometry and acoustic rhinometry]

A cylindrical model consisting of a single or plural acrylic plates with holes of various cross-sectional areas was ventilated by a Harvard pump. Pressure flow curves of the combinations were drawn and analyzed according to the percent expression method. The length of the cylinder through the same cross-sectional area did not influence the ventilatory resistance. Divergent flow toward the downstream part decreased the resistance, but convergent flow from the upstream part did not. Simultaneous setting of convergent flow from the upstream part and divergent flow to the downstream part decreased the resistance most effectively, as much as approximately 70% of the original resistance. Two separately positioned cross-sectional areas in a respiratory circuit increased the resistance about 1.4 times when the separation length was more than 3 cm, while the resistance remained between 1 and 1.4 times when the separation was shorter than 3 cm. The average values of the minimum areas measured by acoustic rhinometry were usually much larger than expected from the present study. One of the factors affecting this difference may be that the axis from the nostril to the choana is complicated enough to significantly modify the aerodynamics of the nasal cavity.