Noninvasive method for detecting laryngeal narrowing with low-frequency sound

Area of Science:

• Respiratory Physiology
• Medical Acoustics

Background:

• Assessing laryngeal resistance is crucial for diagnosing respiratory conditions.
• Current methods for measuring laryngeal resistance can be invasive.

Purpose of the Study:

• To develop a noninvasive method for detecting laryngeal narrowing using low-frequency sound.
• To establish a correlation between sound-pressure amplitude changes and respiratory resistance.

Main Methods:

• Low-frequency sound (800 Hz) was introduced into the mouth of human subjects and dogs.
• Sound-pressure amplitude above (SPAa) and below (SPAb) the vocal cords was measured using neck microphones.
• Respiratory resistance (Rrs) was measured, and the relationship between SPAa and SPAb changes and Rrs was analyzed.

Main Results:

• A strong correlation (r=0.96) was found between the difference in percent changes of SPAa and SPAb (Y) and the increase in respiratory resistance (X) in human subjects (Y = 22.4 X1.20).
• Similar proportions were confirmed in dogs with manually narrowed vocal cords.
• The relationship remained consistent when laryngeal resistance was directly measured, independent of lower airway resistance changes.

Conclusions:

• Increased laryngeal resistance can be accurately detected noninvasively using low-frequency sound analysis.
• This method provides a reliable, noninvasive approach to assess laryngeal narrowing and its impact on respiratory resistance.