MeSH D023842 | ||
Acoustic Rhinometry is a diagnostic measurement of the nose and the nasal cavity through acoustic reflections. It can be used to measure nasal anatomical landmarks, nasal septum deviation, and nasal airway changes in response to allergen provocation tests. This test has been developed from methods that were used to measure lower respiratory tract resistance.
Contents
Method
The test is carried out by generating an acoustic pulse from a speaker or spark source and this sound pulse is transmitted to the nose along a tube. This sound pulse is reflected back to a microphone and this reflection is generated according to the changes in the local acoustic impedance related to cross-sectional area of the nasal cavity. The microphone transmits the sound signal to an amplifier and to a PC which processes it an area distance graph.
These measurements correlate well with area measurements done by CT scans, nasal airway resistance measured by rhinomanometry, but they are sometimes unreliable in the posterior area and when the nasal area is congested.
Advantages
Main advantage of this procedure is that it provides a measure of nasal cross-sectional area with the length of the nasal passage. This cross-sectional area can also be expressed as nasal volume along the nasal passage.
Normal Values
Minimum cross-sectional area of nasal passage within normal levels is 0.7 cm2 which ranges around 0.3-1.2 cm2. During decongestion it can increase to around 0.5-1.3 cm2. Accuracy of this method is dependent on the interface between the nose and the equipment. Mispositioning of the tube or air leaks from there can cause to vary the results.