Measurement reliability of phonation threshold pressure in pediatric subjects

Sensitivity of Phonation Onset Pressure to Vocal Fold Stiffness Distribution

Phonation onset is characterized by the unstable growth of vocal fold (VF) vibrations that ultimately results in self-sustained oscillation and the production of modal voice. Motivated by histological studies, much research has focused on the role of the layered structure of the vocal folds in influencing phonation onset, wherein the outer "cover" layer is relatively soft and the inner "body" layer is relatively stiff. Recent research, however, suggests that the body-cover (BC) structure over-simplifies actual stiffness distributions by neglecting important spatial variations, such as inferior-superior (IS) and anterior-posterior gradients and smooth transitions in stiffness from one histological layer to another. Herein, we explore sensitivity of phonation onset to stiffness gradients and smoothness. By assuming no a priori stiffness distribution and considering a second-order Taylor series sensitivity analysis of phonation onset pressure with respect to stiffness, we find two general smooth stiffness distributions most strongly influence onset pressure: a smooth stiffness containing aspects of BC differences and IS gradients in the cover, which plays a role in minimizing onset pressure, and uniform increases in stiffness, which raise onset pressure and frequency. While the smooth stiffness change contains aspects qualitatively similar to layered BC distributions used in computational studies, smooth transitions in stiffness result in higher sensitivity of onset pressure than discrete layering. These two general stiffness distributions also provide a simple, low-dimensional, interpretation of how complex variations in VF stiffness affect onset pressure, enabling refined exploration of the effects of stiffness distributions on phonation onset.

[Advances in application research on assessment methods of vocal fatigue]

Vocal fatigue（VF） is the common clinical symptom of voice diseases. It can also be a separate symptom and is considered to be a signal for the body to rest and to avoid pathological damage to the vocal cords. Therefore, the early identification and evaluation of vocal fatigue is of great value to the early prevention and treatment of vocal diseases. In recent years, there are many researches on the evaluation methods of vocalization fatigue. We searched the relevant literature and summarized the application status of vocal fatigue assessment methods, in order to provide reference for the selection and development of vocal fatigue assessment tools in clinical practice.

Pediatric Voice Therapy: How Many Sessions to Discharge?

PURPOSE

Voice therapy is the primary treatment for children presenting with benign morphological vocal fold changes. This study examined the number of voice therapy sessions required to meet treatment goals and identified factors that predicted treatment length for pediatric voice patients.

METHOD

An observational cohort design was employed. Data were extracted from the University of Wisconsin-Madison Voice and Swallow Outcome Database. This study examined 62 children who completed a course of voice therapy with a speech-language pathologist (SLP) addressing dysphonia caused by benign vocal fold lesions. Extracted data included patient demographics, auditory-perceptual assessments, acoustic and aerodynamic voice measures, videostroboscopy ratings, and medical comorbidities. Linear regression was used to identify predictors of number of therapy sessions.

RESULTS

Patients received an average of 7.5 sessions of voice therapy prior to discharge. Baseline auditory-perceptual assessment of dysphonia (p = .032), phonation threshold pressure (PTP, p = .005), Glottal Function Index (GFI) score (p = .006), and glottic closure pattern (p = .023) were significant predictors of number of voice therapy sessions. These measures, as well as hourglass glottic closure, predicted longer intervention duration. The regression model had an overall r ² of .62.

CONCLUSIONS

Pediatric voice therapy addressing benign vocal fold lesions and/or laryngeal edema required an average of 7.54 sessions before voice outcomes were sufficiently improved for discharge. More severe overall SLP ratings of dysphonia, GFI scores, PTP, or hourglass glottic closure pattern significantly predicted increased number of therapy sessions prior to discharge. Future work should determine what other factors affect treatment duration and how the efficiency of pediatric voice therapy can be maximized.

Retest Reliability for Complete Airway Interruption Systems of Aerodynamic Measurement

INTRODUCTION

Measures of subglottal pressure (Ps), phonation threshold pressure (PTP), and laryngeal resistance (LR) can be used as indicators of vocal cord disorders. The gold standard non-invasive measurement uses labial interruption, which has been shown to have reliability inconsistencies. Mechanical interruption methods have demonstrated promise in measurement reliability. The goal of the present study is to compare retest reliability of labial and mechanical interruption methods.

METHODS

55 subjects aged 18-69 participated. Ten trials were performed for each method. For labial interruption, subjects produced five labial plosives at comfortable and quiet volumes. For mechanical interruption, subjects produced a sustained /α/ while a balloon valve interrupted phonation five times. Thirty subjects completed a second study visit identical to the first approximately two weeks (15 days ± 3.76) after the first visit. Ps, PTP, mean airflow rate, and LR were determined for each subject and retest reliability for each was analyzed.

RESULTS

The percent difference in measurement results for test-retest of Ps were 12.88% ± 10.15 for mechanical interruption and 27.56% ± 17.14 for labial interruption (P = 0.0003). The percent difference for PTP measurements were 21.46% ± 16.01 for mechanical and 17.04% ± 14.62 (P = 0.3372) for labial. Intra-subject coefficients of variation of Ps were 0.086 ± 0.046 for mechanical and 0.161 ± 0.078 for labial (P < 0.0001). For PTP, the coefficients were 0.177 ± 0.083 for mechanical and 0.186 ± 0.091 for labial (P = 0.5402). Lastly, for LR (Ps divided by mean airflow rate) the percent differences were 14.33% ± 10.06 for mechanical and 53.87% ± 43.19 for labial (P < 0.0001) with intra-subject variability of 0.115 ± 0.050 for mechanical and 0.287 ± 0.222 for labial (P < 0.0001).

CONCLUSIONS

Ps and LR measured using mechanical interruption showed more consistency for both retesting across separate study visits and intra-subject variability. PTP was similar in retesting and intra-subject variability. Continued work to improve mechanical interruption techniques is warranted as these methods offer higher reliability and consistency than the labial interruption methods.

Age and Sex Comparison of Aerodynamic Phonation Measurements Using Noninvasive Assessment

Purpose The goal of this study was to present vocal aerodynamic measurements from pediatric and adult participant pools. There are a number of anatomical changes involving the larynx and vocal folds that occur as children age and become adults. Data were collected using two methods of noninvasive aerodynamic assessment: mechanical interruption and labial interruption. Method A total of 154 participants aged 4-24 years old took part in this study. Ten trials were performed for both methods of airway interruption. To perform mechanical interruption, participants phonated /α/ for 10 s trials while a balloon valve interrupted phonation 5 times. For labial interruption, participants said /pα/ 5 times at comfortable and quiet volumes. Aerodynamic measures included subglottal pressure, phonation threshold pressure, mean airflow, laryngeal resistance, and others. Results One hundred one participants (51 females) successfully completed testing with both methods. Eight out of 20 measurements were found to have a statistically significant effect of participant age on measurements. Sex alone had a significant effect on vocal efficiency for the labial quiet method. Conclusions The data discussed here can be used to view age and sex trends in vocal aerodynamic measurements. When using either method of mechanical or labial interruption, participant age needs to be taken into account to properly interpret several aerodynamic parameters. A participant's sex is not as important when using these methods.