Acoustic Rhinometry

1. Nosepieces with different diameters are used for nostrils of different sizes (Adult 12mm & 10mm, Veterinary, Conical, and Pediatric). It is important that the nosepiece has a good seal around the nostril, and great precaution is taken to avoid deformation of the vestibulum nasi by applying too much pressure.
2. Measurements can be done congested or decongested. To obtain maximum decongestion, wait 10 minutes for the next test after spraying the nasal passages, do not decongest before a baseline test. (AAAAI position statement).
3. Have the patient clear the nasal passages by blowing their nose.
4. Attach the nosepiece and hold the sound tube approximately 30-45 degrees from the ground.
5. Click on the Acquisition icon at the top of the screen - some systems may require a calibration for each test based on manufacturer's recommendations.
6. When you are happy with positioning, ask the subject to take a breath in and hold their breath. Each test will range in the time it takes to obtain a tracing. Ask them to do that and then click on the start/red button to take in data.
7. Over the next couple of seconds curves will show on the screen, after which you can remove the sound tube from the subject. Curves can be viewed, and if required, deselected by using the tick boxes on the right side of the screen. The Gray Curve is a “normal” wave for comparison on some systems.

Factors Affecting Accuracy

• Calibration

• Background Noise: Use in an environment less than 65dB

• Angle of Probe: Aim at the angle of the floor of the noise, usually 30-degree angle

• Patient co-operation: Hold breath during the measurement. Breathing causes movement of the non-cartilaginous tissue affecting the sound wave

• Nosepiece/nose seal: Use a gel and place at the anatomical angle of the nare.
  

• Nasal volume differences are more sensitive than the MCA in adults and kids.

• Left+Right is averaged to minimize the risk of the nasal cycle affecting the final result.

• The phenomenon of nasal cycling is present in 80% of most adults.

• Nasal turbinates grow faster than the facial skeletal causing a decrease in the cross-sectional area.



• Many aspects of measuring should be considered to include racial, environmental, and developmental differences. 
  

• If the cross-sectional area is reduced by 33% from the normal value, nasal breathing becomes compromised.

• The cross-sectional area found to be functionally important for nasal breathing is at least 0.32cm²  at approximately 1.4 cm from the nostril opening, or the narrowest portion of the nose at the nasal valve.

• Levels below 0.4 cm² is found to be associated with partial mouth breathing to reduce upper airway resistance.

• Nasal volume 1.5-3.5, or 0-3 cm is the best volume for measurement in kids due to the opening of the sinuses at 4 cm and pulse reflection screwing the measurement.

• Nasal volume 2-5 cm is the most sensitive area for patency after decongestion and best measurement consideration.

• Nasal volume 5-10 cm include information on the open sinuses.



• Decongestion increases the total volume of the nasal cavity by 35%.