閉塞型睡眠時無呼吸症候群の低呼吸に伴う気管音の検討 : 特に低呼吸に伴うイビキ音の特徴について

Abstract

The author analyzed night tracheal sounds of hypopnea events in 12 patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). Tracheal sounds were recorded on a video tape recorder through a microphone attached to the anterior neck over the trachea during overnight polysomnography. In each patient ten hypopnea episodes were selected for analysis. Tracheal sounds were analyzed using sound-spectrogram and power spectra. Mean power spectra of inspiratory and expiratory tracheal sounds within a bandwidth of 100 to 2000 Hz were respectively calculated for 3 breaths preceding and following hypopneas as well as during hypopneas. On inspection of sound-spectrogram, the snoring sounds were observed frequently in the inspiratory phase, especially during hypopnea(91%). Next, when the snoring sound was excluded and only the breath sound was examined, power spectra of tracheal sounds during hypopnea were significantly decreased for both the inspiratory and expiratory phases compared to those while awake (p＜0.001). When snoring sounds were not excluded and all tracheal sounds were examined, the power spectra of inspiratory tracheal sounds not only preceding and following hypopnea but also during hypopnea were significantly higher than those while awake, because of the presence of snoring sounds (p＜0.01). Next, the author compared snoring sounds in 10 OSAHS patients with those in 5 simple snorers. On inspection of sound-spectrogram, the variability of snoring was significantly higher in OSAHS patients than in simple snorers (p＜0.005). In quantitative analysis of power spectra, the coefficient of variation of the power of the snoring sounds in OSAHS patients was significantly higher than that in simple snorers (p＜0.001). The author concludes that the characteristics of tracheal sounds during hypopnea events in OSAHS patients are the presence of inspiratory snoring sound and high variability of the snoring sounds.