Measurement of upper airway dimensions during inspiratory flow

We examined the effectiveness of two-microphone acoustic reflection pharyngometry in determining the changes in the human upper airway collapsible segment during steady inspiratory flow conditions. Differences in oral airway dimensions of a male subject, at 3 flow levels, were analyzed. The physiological data, then, was applied to a mathematical model of airway collapse, and the coefficient of collapse (C_c) was calculated. The collapsible segment was approximately 10 cm in length, and was located between the oro-pharyngeal junction (OPJ), and the glottis; the entire segment was susceptible to area decrease at a flow rate of 500 ml/s. C_c calculation indicated that full collapse would not occur during our experimental conditions, which was validated by pharyngometry