Measurement of the Nasal Airway

The nasal airway can be considered as a simple tube, and measurement of the airflow through the tube and its driving pressure, by means of rhinomanometry, can provide a measure of nasal patency. The prime factor determining nasal patency is the cross sectional area of the nasal airway and this can be measured by means of acoustic rhinometry. Rhinomanometry provides a functional measure of nasal patency, whereas acoustic rhinometry provides an anatomical measurement of cross sectional area or nasal volume. Nasal resistance to air flow is calculated from two measurements: nasal airflow and trans-nasal pressure. Active rhinomanometry involves the generation of nasal airflow and pressure with normal breathing. The peak inspiratory or expiratory airflow through the nose associated with maximal respiratory effort can be used as a measure of nasal conductance. The measurement is effort dependent and is less sensitive than rhinomanometry or acoustic rhinometry in determining small changes in conductance.