Acoustic rhinometry uses sound pulses transmitted into the nose to measure nasal cavity cross-sectional areas along its length. Reflected sound pulses are detected and analyzed to generate area-distance graphs. It provides more detailed anatomic information than rhinomanometry. Measurements correlate well with CT scans and nasal resistance. However, accuracy decreases in the posterior nose, especially when congested. Normal minimum cross-sectional areas are around 0.7 cm2 increasing to 0.9 cm2 after decongestion. Results graphs show areas before and after decongestion with recorded CSA values compared to norms.

1. ACOUSTIC RHINOMETRY
Prepared by
Dr. Saef M. Duhies

2. Scott-Brown's Otorhinolaryngology, Head and Neck Surgery 7th edition
Ronald Eccles BSe PhD DSe
Director, Common Cold Centre and
Healthcare Clinical Trials
Cardiff School of Biosciences
Cardiff University
Cardiff, Wales, UK
Cummings Otolaryngology Head & Neck Surgery 5th EDITION
John Pallanch, M.D.
Assistant Professor
Department of Otolaryngology
Mayo School of Graduate Medical Education
Chair
Division of Rhinology
Department of Otorhinolaryngology
Mayo Clinic
Rochester, Minnesota

3. Acoustic rhinometry consists of generating an acoustic pulse from a spark source or speaker and the sound
pulse is transmitted along a tube into the nose.
The sound pulse is reflected back from inside the nose according to changes in the local acoustic
impedance which are related to the cross-sectional area of the nasal cavity.
The reflected sound is detected by a microphone, which transmits the sound signal to an amplifier and
computer system for processing into an area distance graph.
The cross-sectional area measurements obtained with acoustic rhinometry correlate extremely well with
area measurements made by computed tomography scans, and nasal airway resistance measured by
rhinomanometry,
the accuracy of acoustic rhinometry is unreliable in the posterior part of the nose, especially when the
nasal passage is congested.

4. advantage
• it provides a measure of nasal crosssectional area along the length of
the nasal passage, unlike rhino manometry which is limited to
measuring the narrowest point of the nasal airway.
• The plot of crosssectional area against distance can also be expressed as
nasal volume for given distances along the nasal passage.
• Rhinomanometry determines nasal patency in terms more
representative of how difficult it is for a person to breathe, while
acoustic rhinometry is preferable to study nasal volume changes. Both
methods can give information about a site of obstruction, but acoustic
rhinometry gives more precise anatomic information

5. Normal values for acoustic rhinometry
•minimum cross-sectional area for a nasal passage
is 0.7 cm2 with a range from 0.3 to 1.2 cm2
•on decongestion this increases to 0.9 cm2 with a
range from 0.5 to 1.3 cm2.

6. Reporting Results
• The graph is usually printed with results
“before” and “after” decongestion;
• cross-sectional areas CSA1, CSA2, CSA3, and
estimated volume are recorded.
• CSA1 is usually the nasal valve area; CSA2
may be located at the anterior head of the
inferior and/or middle turbinate. CSA3 is the
mid-posterior end of the middle turbinate
• The congestion factor may be calculated and
the sides compared with each other.
• The values of CSA1, CSA2, and CSA3 are
recorded and compared with normative
values.