LXXIX Considerations in the Measurement of Nasal Patency

Abstract

Relative changes in nasal patency may be quantitatively assessed by methods which relate nasal air flow to the associated pressure head across the nasal passages. The resulting data may reflect both viscous losses and dynamic effects relating to gas inertia and to gas velocity at sampling points. Except at the lowest rates of flow, the nasal dP-[flow rate]Q relationship is markedly non-linear; for each half of expiration, a transnasal pressure difference (dP)=k1Q2 + k2Q + k3 expression has been found valid. Nasal airway resistance steadily increases with flow rate making sequential determinations comparable only when a common flow rate is used. As nasal patency decreases, the value dP/Q becomes progressively less satisfactory as an estimator of true resistance, delta dP/delta Q. In addition to considerations arising from gas dynamics, measurement procedures must weigh the consequences of nasal manipulation, alar motion, impaired mucosal ventilation and obstruction of nasal vascular outflow.