Flow characteristics as a function of velopharyngeal gap size

Abstract

The classic paradigm for treatment of velopharyngeal insufficiency (VPI) is based on the assumption that the severity of the speech disorder correlates with the size of the velopharyngeal (VP) opening. However, several studies have documented that even small VP openings can cause significant speech distortion. To investigate the potential contribution of aeroacoustic sources to speech distortion in VPI-affected speech, we set out to determine how airflow characteristics change as a function of the VP gap size. To do so, a head and neck CT scan of a VPI patient sustaining the phoneme /z/ was obtained. From the CT scan, patient-specific phantoms of the upper airway were made extending from the glottis to the nasal and oral exits. Four phantoms were made: one with the original VP gap size and three with VP gap sizes artificially scaled by factors of 1.25, 1.5, and 2. Particle image velocimetry (PIV) was used to measure the velocity and turbulence fields along planar slices in each phantom. Average velocity fields for each VP gap size are presented, and the change in flow characteristics as a function of the VP gap size is discussed, along with the implications for aeroacoustic sources.