Relationship Between Forced Expiratory Flow and Tracheal Sound

• Published in: Nihon Kyōbu Shikkan Gakkai zasshi Vol. 25; no. 4; pp. 451 - 456
• Main Authors: Koike, Shigeo, Ono, Mariko, Iguchi, Mani, Hisada, Tetsuya, Mori, Masashi, Ide, Mariko, Nagata, Taiji, Kino, Hiroyoshi, Sugimoto, Tsuneaki, Horiuchi, Tadashi
• Format: Journal Article
• Language: Japanese
• Published: Japan The Japanese Respiratory Society 01.04.1987
• Subjects: Adult; Choking; Female; Flow limitation; Forced Expiratory Flow Rates; Humans; Male; Middle Aged; Respiratory Sounds; Trachea - physiology
• ISSN: 0301-1542; 1883-471X
• DOI: 10.11389/jjrs1963.25.451

Both tracheal sound and flow were measured simultaneously during forced expiration in thirteen subjects (eleven normal, one with bronchial asthma, and one with emphysema). The tracheal sound was recorded at the neck over the trachea by a condenser microphone (ECM 150, SONY) and the flow was measured by a hot-wire anemometer (AS 4500, Minato). The signals were recorded on an FM tape recorder, low-pass filtered (cut-off frequency: 2kHz), digitized (sampling frequency: 5kHz) and the power spectra of tracheal sounds were obtained by fast Fourier transform (1024 or 512 points). In every subject we observed the development of line spectra in the forced expiratory tracheal sounds, the frequencies of which ranged between 0.419 to 1.084kHZ. There was a positive correlation (r=0.85) between the peak flows (FEFmax) and these frequencies. We speculate that these line spectra were generated by vortices in the upper airways and that the pressure drop caused by vortices plays in important role in the flow limitation during forced expiration.