VOCALIZATION SUBSYSTEM RESPONSES TO A TEMPORARILY INDUCED UNILATERAL VOCAL FOLD PARALYSIS

Healthy voicing is thought to be dependent on a dynamic balance of three interactive subsystems: respiration, phonation, and resonance. Theoretically, multiple patterns of subsystem interactions likely underlie healthy voice production; however surprisingly little quantitative data exists defining the nature of these subsystem production patterns and interactions across individuals. The central aim of this study was to quantify the interactions of the vocalization subsystems in a non-perturbed and perturbed condition (induced unilateral vocal fold paralysis) in 10 vocally healthy participants. Respiratory inductance plethysmography, laryngeal aerodynamics, and acoustic formant data were used to measure the proportional contributions of, and changes to, the three vocal subsystems during voice production tasks. The overall hypothesis was that individuals would demonstrate distinctive patterns of change in voice subsystem interaction across vocalization conditions, resulting in characteristic vocalization profiles. Using Dynamics Systems Theory (DST) as a guide, we hypothesized that analysis of group data alone would hide important individual variability that would help better understand differences in subsystem regulation across individuals. Additionally, in accordance with DST, we hypothesized that although there would be individual variability during voice production tasks, only a small group of characteristic subsystem patterns would emerge, permitting subgrouping of individuals into unique vocalization profiles. Results demonstrated that group data masked important aspects of individual performance. Despite all individuals demonstrating paramedian paralysis on visualization during the perturbation phase, unique subsystem patterning strategies for coping with the acute vocal fold paralysis were observed. Despite individual variability, subgroups were able to be determined which revealed commonalities in the dominant physiologic strategies of subsystem regulation across individuals. A dynamic systems state space model was constructed as a visual aid to demonstrate that the changes noted between voicing conditions were not random, but rather formed specific trajectories. Implications for translation of these results into clinical practice are discussed

Reliability of Clinical Office-Based Laryngeal Electromyography in Vocally Healthy Adults

Objective: This study aimed to conduct a 3-session reliability assessment of the laryngeal electromyography (LEMG) signal in healthy participants during intensity controlled vocalization tasks. We hypothesized that vocal intensity level and testing session would affect LEMG measures. Methods: This prospective study used a 2-factor repeated measures design. Seven participants underwent bipolar needle LEMG of the right thyroarytenoid muscle. Data were collected over 3 testing sessions using vocalization tasks performed with visually guided intensity feedback targets (65 and 75 dB SPL). Root mean square amplitudes in microvolts were analyzed for within-session and between-session reliability. Results: The main effect for intensity was found to approach significance (F = 5.71, P = .054). However, intraclass correlation coefficients (ICCs) using a 2-factor mixed random effect model indicated poor to fair signal reliability between testing sessions (ICC = 0.56 at 65 dB, 0.40 at 70 dB). Intraclass correlation coefficients for within-session data indicated excellent reliability for all testing conditions (0.84–0.98). Conclusion: Using a quantitative analysis protocol to inform an essentially qualitative technique, our results indicated that there was generally poor to fair reliability in the LEMG signal over testing sessions. Vocal intensity was an important variable that affected LEMG signal reliability. Standardization of LEMG protocols using vocal control parameters and quantitative analyses may help improve LEMG reliability in clinical settings

Vocalization subsystem responses (Croake et al., 2018)

<div><b>Purpose: </b>The purpose of this study is to quantify the interactions of the 3 vocalization subsystems of respiration, phonation, and resonance before, during, and after a perturbation to the larynx (temporarily induced unilateral vocal fold paralysis) in 10 vocally healthy participants. Using dynamic systems theory as a guide, we hypothesized that data groupings would emerge revealing context-dependent patterns in the relationships of variables representing the 3 vocalization subsystems. We also hypothesized that group data would mask important individual variability important to understanding the relationships among the vocalization subsystems.</div><div><b>Method: </b>A perturbation paradigm was used to obtain respiratory kinematic, aerodynamic, and acoustic formant measures from 10 healthy participants (8 women, 2 men) with normal voices. Group and individual data were analyzed to provide a multilevel analysis of the data. A 3-dimensional state space model was constructed to demonstrate the interactive relationships among the 3 subsystems before, during, and after perturbation.</div><div><b>Results:</b> During perturbation, group data revealed that lung volume initiations and terminations were lower, with longer respiratory excursions; airflow rates increased while subglottic pressures were maintained. Acoustic formant measures indicated that the spacing between the upper formants decreased (F3–F5), whereas the spacing between F1 and F2 increased. State space modeling revealed the changing directionality and interactions among the 3 subsystems.</div><div><b>Conclusions: </b>Group data alone masked important variability necessary to understand the unique relationships among the 3 subsystems. Multilevel analysis permitted a richer understanding of the individual differences in phonatory regulation and permitted subgroup analysis. Dynamic systems theory may be a useful heuristic to model the interactive relationships among vocalization subsystems.</div><div><br></div><div><b>Supplemental Material S1.</b> Intraclass correlation coefficients (ICCs) with 95% confidence intervals (CIs).</div><div><br></div><div><b>Supplemental Material S2. </b>Descriptive statistics: group means, standard deviations, and ranges by condition (pre recurrent laryngeal nerve [RLN] block [PRE], during RLN block [DUR], and post-RLN block recovered [REC]).</div><div><br></div><div><b>Supplemental Material S3.</b> Repeated measures analysis of variance (ANOVA). Tukey’s honestly significant difference test was applied to determine significant differences between conditions. **<i>p</i> < .05. </div><div><br></div><div>Croake, D. J., Andreatta, R. D., & Stemple, J. C. (2018). Vocalization subsystem responses to a temporarily induced unilateral vocal fold paralysis. <i>Journal of Speech, Language, and Hearing Research, 61,</i> 479–495. https://doi.org/10.1044/2017_JSLHR-S-17-0227</div