Acoustic characterization of upper airway variations from wakefulness to sleep with respect to obstructive sleep apnea

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ORIGINAL ARTICLE

Acoustic characterization of upper airway variations from wakefulness to sleep with respect to obstructive sleep apnea Farahnaz Hajipour 1

&

Eleni Giannouli 2 & Zahra Moussavi 1,3

Received: 7 February 2020 / Accepted: 18 July 2020 # International Federation for Medical and Biological Engineering 2020

Abstract The upper airway (UA) is in general thicker and narrower in obstructive sleep apnea (OSA) population than in normal. Additionally, the UA changes during sleep are much more in the OSA population. The UA changes can alter the tracheal breathing sound (TBS) characteristics. Therefore, we hypothesize the TBS changes from wakefulness to sleep are significantly correlated to the OSA severity; thus, they may represent the physiological characteristics of the UA. To investigate our hypothesis, we recorded TBS of 18 mild-OSA (AHI < 15) and 22 moderate/severe-OSA (AHI > 15) during daytime (wakefulness) and then during sleep. The power spectral density (PSD) of the TBS was calculated and compared within the two OSA groups and between wakefulness and sleep. The average PSD of the mild-OSA group in the low-frequency range (< 280 Hz) was found to be decreased significantly from wakefulness to sleep (p-value < 10−4). On the other hand, the average PSD of the moderate/severeOSA group in the high-frequency range (> 900 Hz) increased marginally significantly from wakefulness to sleep (p-value < 9 × 10−3). Our findings show that the changes in spectral characteristics of TBS from wakefulness to sleep correlate with the severity of OSA and can represent physiological variations of UA. Therefore, TBS analysis has the potentials to assist with diagnosis and clinical management decisions in OSA patients based on their OSA severity stratification; thus, obviating the need for more expensive and time-consuming sleep studies.

Keywords Obstructive sleep apnea . Tracheal breathing sounds . Power spectral analysis . Acoustic investigation Abbreviations AHI Apnea/hypopnea index ANOVA analysis of variance BMI Body mass index HSS Home sleep study MRI Magnetic resonance imaging NC Neck circumference OSA Obstructive sleep apnea PSD Power spectrum density PSDavg Average power spectrum density PSG Polysomnography * Farahnaz Hajipour [email protected] 1

Biomedical Engineering Program, University of Manitoba, Winnipeg, MB, Canada

2

Department of Internal Medicine, Section of Respirology, University of Manitoba, Winnipeg, MB, Canada

3

Department of Electrical & Computer Engineering, University of Manitoba, Winnipeg, MB, Canada

SE SVM TBS UA

Standard error Support vector machine Tracheal breathing sounds Upper airway

1 Introduction The upper airway (UA) is a collapsible structure; it dynamically changes from wakefulness to sleep, and also between the sleep stages [1]. The patency of the UA is suggested to be dependent on the equilibrium between the dilating forces generated by the UA dilator muscles and the pressure exerted by the heterogeneous surrounding soft tissue [2]. The complete or partial collapse of the