Moussavi added that detecting OSA through sound analysis could become an attractive alternative to the more costly and labor-intensive method of performing overnight polysomnography. Data were digitized and then analyzed using spectral and waveform fractal dimension techniques. The breathing sounds were picked up by a microphone placed over the neck, and the recordings were repeated in two body positions: sitting upright and lying on the back. Then the process was repeated as they breathed through their mouth with a nose clip in place.
The subjects were instructed to breathe through their nose at their normal breathing level for at least five breaths and then breathe at their maximum flow level for another five breaths. The presence or absence of OSA was validated by full-night polysomnography. Moussavi and co-investigator Aman Montazeri studied 35 patients with varying severity levels of OSA and 17 age-matched controls. "Despite being able to breathe at the same high flow rate, the pharyngeal pressure in people with OSA during wakefulness is usually more negative than that in the non-OSA group," said principal investigator and lead author Zahra Moussavi, PhD, professor and Canada Research Chair on Biomedical Engineering at the University of Manitoba in Winnipeg, Canada. Breathing sounds are directly related to pharyngeal pressure, making sound analysis a viable diagnostic option for OSA. Sound analysis also allowed for the stratification of OSA severity.Īccording to the authors, people with OSA tend to have a narrower and more collapsible pharynx with more negative pharyngeal pressure, which creates greater resistance when breathing through the nose. In an analysis that combined the two most significant sound features, the presence or absence of OSA was predicted with more than 84-percent accuracy. Results show that several sound features of breathing were statistically significant between participants with obstructive sleep apnea and healthy controls.
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