A Comparison of Indirect and Direct Methods for Estimating Transglottal Airflow Rate

Objective: The purpose of this study was to compare indirect estimates of transglottal airflow rate using measures of phonation quotient with direct measures of mean airflow rate derived from a pneumotachograph. Study design: This study used prospective, repeated measures design. Methods: Nineteen male and female participants, matched for age, completed tasks for maximum phonation time and vital capacity in addition to the comfortable sustained phonation protocol of the Phonatory Aerodynamic System (PAS), Model 6600. Phonation quotient was calculated from the vital capacity and phonation time measures, whereas actual transglottal airflow was obtained from the flow waveforms recorded on the PAS system. Statistical analyses compared transglottal airflow rate measures as a function of instrument and separately as a function of gender. Results: Statistically significant differences were present only as a function of gender on airflow measures but not as a function of the instrument. There were no interaction effects present between instrument and gender. Conclusions: Phonation quotient can be used as an estimate of transglottal airflow in the absence of a pneumotachograph-based system.