Obstructive sleep apnoea (OSA) is a breathing disorder in sleep with immensely multiscale and multifactorial etiology. The disorder is not completely understood yet and requires further attention of researcher in different branches of science. Adopting coupled computational FSI simulation of airflow in human upper airway, an attempt to explain palatal flutter and onset of obstructive pharyngeal collapse was made. The focus was put on the velopharyngeal region where the greatest level of upper airway compliance was estimated to occur. It was showed that during the inspiratory phase of breathing velopharyngeal narrowing due to subatmospheric suction pressure occurs. Conversely, pharyngeal widening was predicted during the expiration because of the positive gauge pressure. As the main attribute of snoring, simultaneous soft palate flutter of frequency 17.8 Hz was predicted. It was shown the evaluated vibrations were not because of the unstableness of the used numerical coupling scheme. When the length scale of observation is reduced the two-phase nature of respiratory fluid flow is exposed. Hence, the twice-coupled system needs to be analysed. The experimental system was developed and built mimicking the fundamental characteristics of the respiratory system - turbulent jet, flow recirculation, and liquid-lined compliant wall. It was demonstrated the damping of shear and pressure fluctuations was increased in consequence of increase in liquid film thickness, viscosity or surface tension. Hence, altering airway surface liquid physical properties, stimuli and activation of mechanoreceptors could be modulated affecting the onset of obstructive sleep apnoea.
|
