Evaluation of vocal efficiency in voice disorders by calculation of intrapulmonic pressure

Abstract

Vocal efficiency was investigated by simultaneously measuring the intrapulmonic pressure, the mean flow rate and the sound intensity. The intrapulmonic pressure during sustained phonation has been successfully and noninvasively calculated with a pneumotachograph and a body plethysmograph. Normal and disordered subjects were examined, and the variation of vocal efficiency for each patient from the averaged values of ten normal subjects was investigated. The vocal efficiency is represented by a ratio of the sound power to the aerodynamic power, and the aerodynamic power is expressed in terms of intrapulmonic pressure times mean flow rate. The result suggests that the variation of vocal efficiency can reprepsent overall severity of the voice disorder. The relative contributions of intrapulmonic pressure and mean flow rate to the efficiency can classify the pathological lesions into three types such as leakage of air through the glottis, a mass on the vocal fold, and the stiffness of the vocal fold.