An experimental investigation on the effect of airflow on the sound generated in a simplified tube with a constriction representing trachea for obstructive sleep apnea diagnosis during wakefulness

Abstract

Obstructive sleep apnea (OSA) diagnosis using tracheal breathing sounds analysis during wakefulness has already shown a great potential with an accuracy of 84.5% compared to gold-standard polysomnography (PSG). The inclusion of geometrical parameters to acoustic diagnosis of OSA during wakefulness may not only increase the accuracy but also give an insight into OSA pathology. In this study, we aimed to develop an upper airway model for flow-sound relationship in the presence of a constriction (e.g. increased airway stiffness and/or collapsibility). The geometrical change selected for this study is a circular constriction representing tracheal narrowing. An experimental measurement was conducted on a 3D printed model of a tube with a constriction while recording the airflow-generated sound at three locations. Several constriction sizes were tested at different airflow rates. The results show a higher frequency shift for the resonating frequencies for the smaller constrictions. In addition, Larger slopes of the logarithmic relationship between airflow and the generated sounds’ power were observed for the larger constrictions. These findings are encouraging for future studies to evaluate the mathematical relationship between the tracheal breathing sounds at the presence of different constriction sizes for a realistic upper airway geometry.