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

Mean flow rate (MFR) and laryngeal resistance (R_L) 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 R_L measurement reliability in a pediatric population using labial and mechanical interruption methods.

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. R_L was calculated by dividing subglottal pressure (P_s) by MFR. The primary outcome measures of this study were the coefficients of variation of MFR and R_L. 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.

Mean P_S (t(38) = 2.966, P < 0.01) and R_L (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 R_L (t(38) = 3.439, P < 0.01) while there was no difference in P_S variability (P = 0.260). Mean MFR and R_L were related to age for both the labial (MFR: r = 0.588, P < 0.001; R_L: r = -0.468, p = 0.003) and mechanical trials (MFR: r = 0.534, P < 0.001; R_L: r = -0.496, P = 0.001). The coefficients of variation for R_L 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 P_S was only correlated in the mechanical trials (r = -0.519, P = 0.001).

Differences in means and intrasubject variation are likely due to differences in task and measurement timing. Precision of MFR and R_L 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.