Measurement Reliability of Laryngeal Resistance and Mean Flow Rate in Pediatric Subjects.

OBJECTIVE: Mean flow rate (MFR) and laryngeal resistance (RL ) are sensitive to changes in glottal configuration and biomechanics. There is little reported on aerodynamic parameters in children. We conducted a pilot study to evaluate MFR and RL measurement reliability in a pediatric population using labial and mechanical interruption methods.

METHOD: Thirty-nine subjects aged 4-17 performed 10 trials per method. For labial interruptions, subjects produced five labial plosives at a comfortable amplitude. For mechanical interruptions, subjects maintained a steady /α/ while a balloon valve interrupted their airflow five times for 250 milliseconds each. MFR was measured as the flow through the interruption device between interruptions. RL was calculated by dividing subglottal pressure (Ps ) by MFR. The primary outcome measures of this study were the coefficients of variation of MFR and RL . Paired t tests were used to compare each variable between the two methods. Pearson's correlation was used to analyze the relationship between each parameter and subject age.

RESULTS: Mean PS (t(38) = 2.966, P < 0.01) and RL (t(38)=3.563, P < 0.01) were higher for labial interruptions while mean MFR (t(38) = -2.036, P < 0.05) was lower. Intrasubject coefficients of variation were higher for the labial technique for both MFR (t(38) = 4.939, P < 0.001) and RL (t(38) = 3.439, P < 0.01) while there was no difference in PS variability (P = 0.260). Mean MFR and RL were related to age for both the labial (MFR: r = 0.588, P < 0.001; RL : r = -0.468, p = 0.003) and mechanical trials (MFR: r = 0.534, P < 0.001; RL : r = -0.496, P = 0.001). The coefficients of variation for RL were negatively correlated with age for both labial (r = -0.415, P = 0.009) and mechanical trials (r = -0.471, P = 0.002). MFR was only correlated in the labial trials (r = -0.514, P = 0.001) and PS was only correlated in the mechanical trials (r = -0.519, P = 0.001).

CONCLUSIONS: Differences in means and intrasubject variation are likely due to differences in task and measurement timing. Precision of MFR and RL measurement in pediatric subjects was higher for mechanical interruption; further exploration of this method and its clinical utility is warranted. Measurement of aerodynamic parameters may be a useful addition to pediatric voice assessment.