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