Thursday, March 03 2011 @ 11:02 am IST
Contributed by: drtbalu
External nasal valve
Internal nasal valve
Role of Fourier analysis in the study of nasal airflow:
According to Fourier the French scientist any complicated wave form can be expressed as a series of two or more simple sine waves and cosine waves.
Sound generated by air passing through nasal cavity can be recorded by placing probes containing microphone in the anterior nasal cavity. These recorded sounds are subjected to fast fourier transformation using the software called Odisoft rhino.
The recorded frequency spectrum could be classified into:
Low frequency (500 – 1000Hz)
Medium frequency (1-2KHz)
High frequency (3-6 Khz)
Before emarking on recording nasal sounds, the following things should be ensured:
The patient should be completely relaxed
Crusts and mucous secretions from the nasal cavity should be removed
While testing the right nasal cavity the probe is held in the right hand and parallel to the right nasal cavity, while the left hand is used to close the left nasal cavity.
The probe should not be inserted into the nasal cavity and atleast 1 cm space should be there between the probe and the nares.
Recording usually starts during non forced expiration.
Recording should ideally be performed in quiet environment and acoustic artifacts like noise caused by rubbing of wires should be avoided.
Nasal sound analysis:
The frequency and amplitude of the recorded sounds should be taken into consideration. Nasal sound frequency and amplitude increases as the turbulence inside the nasal cavity increases. Nasal sound recordings in patients with deviated nasal septum have shown that the intensity of sound in lower and mid frequencies are not raised that much while the intensity of sound in high frequency was significanty elevated.
Obstruction in nasal valve area can be assessed by performing the Cottles Maneuver. Before cottle's maneuver the intensitey of sound in high frequency is elevated, while recordings performed during cottle's maneuver shows a reduction in the intensity of sound at high frequencies as the nasal air flow assumes a laminar pattern.
This whole system can also be used as a web based diagnostic service, where a patient can be asked to use the probe and the recorded sound is transmitted through internet to the diagnostic server where these sounds can be analysed and diagnosis can be made.