Direct measurement of planar flow rate in an excised canine larynx model.

OBJECTIVES/HYPOTHESIS During phonation, skewing of the glottal flow waveform (Q) refers to a phenomenon that occurs when the flow decelerates more rapidly than it accelerates. This skewing is clinically important because it increases the glottal efficiency, which is defined by the acoustic intensity (sound pressure level) divided by the subglottal pressure. Current theoretical models predict that the only mechanism to cause skewing of Q involves changes in the vocal tract inertance. The purpose of the current work is to show that other factors at the vocal fold level can also cause skewing of Q and to determine if the acoustic intensity is correlated with maximum flow declination rate. STUDY DESIGN Basic science. METHODS Intraglottal geometry and velocity measurements were taken in five canine larynges at the mid-membranous plane using 2-dimensional particle imaging velocimetry (PIV). The flow rate at the glottal exit was computed from the PIV measurements for low, medium, and high subglottal pressures. RESULTS Vortices form in the superior aspect of the divergent glottis during closing. These vortices produce negative pressure that increases both the maximum value of Q and the rapid deceleration of the flow. The skewing of the flow rate is increased as the intraglottal vortices are increased by increasing the subglottal pressure. The increase in the acoustic intensity is highly correlated with certain properties of the flow rate waveform, such as maximum flow rate. CONCLUSION Flow skewing and the acoustic intensity can be increased by increasing the intraglottal vortices. LEVEL OF EVIDENCE N/A.