Carolyn K. Novaleski

Test-Retest Reliability for Aerodynamic Measures of Voice

OBJECTIVES/HYPOTHESIS The purpose of this study was to investigate the intrasubject reliability of aerodynamic characteristics of the voice within typical/normal speakers across testing sessions using the Phonatory Aerodynamic System (PAS 6600; KayPENTAX, Montvale, NJ). METHODS Participants were 60 healthy young adults (30 males and 30 females) between the ages 18 and 31 years with perceptually typical voice. Participants were tested using the PAS 6600 (Phonatory Aerodynamic System) on two separate days with approximately 1 week between each session at approximately the same time of day. Four PAS protocols were conducted (vital capacity, maximum sustained phonation, comfortable sustained phonation, and voicing efficiency) and measures of expiratory volume, maximum phonation time, mean expiratory airflow (during vowel production) and target airflow (obtained via syllable repetition), peak air pressure, aerodynamic power, aerodynamic resistance, and aerodynamic efficiency were obtained during each testing session. Associated acoustic measures of vocal intensity and frequency were also collected. All phonations were elicited at comfortable pitch and loudness. RESULTS All aerodynamic and associated variables evaluated in this study showed useable test-retest reliability (ie, intraclass correlation coefficients [ICCs] ≥ 0.60). A high degree of mean test-retest reliability was found across all subjects for aerodynamic and associated acoustic measurements of vital capacity, maximum sustained phonation, glottal resistance, and vocal intensity (all with ICCs > 0.75). Although strong ICCs were observed for measures of glottal power and mean expiratory airflow in males, weaker overall results for these measures (ICC range: 0.60-0.67) were observed in females subjects and sizable coefficients of variation were observed for measures of power, resistance, and efficiency in both men and women. Differences in degree of reliability from measure to measure were revealed in greater detail using methods such as ICCs and coefficients of variation than with means comparison testing. The results of this study also show that reliable aerodynamic and associated measures may be elicited using comfortable pitch and loudness. CONCLUSIONS The 1-week test-retest reliability for the majority of aerodynamic and associated acoustic measures assessed in this study is considered good-to-excellent. Clinicians and researchers using aerodynamic and associated measures should be aware of possible significant gender effects that influence both normative expectations as well as the standard error of measurement (ie, typical error) and estimates of minimum difference that may be used to differentiate typical from disordered voice.

Quantification of acute vocal fold epithelial surface damage with increasing time and magnitude doses of vibration exposure.

Because the vocal folds undergo repeated trauma during continuous cycles of vibration, the epithelium is routinely susceptible to damage during phonation. Excessive and prolonged vibration exposure is considered a significant predisposing factor in the development of vocal fold pathology. The purpose of the present study was to quantify the extent of epithelial surface damage following increased time and magnitude doses of vibration exposure using an in vivo rabbit phonation model. Forty-five New Zealand white breeder rabbits were randomized to nine groups and received varying phonation time-doses (30, 60, or 120 minutes) and magnitude-doses (control, modal intensity phonation, or raised intensity phonation) of vibration exposure. Scanning electron microscopy and transmission electron microscopy was used to quantify the degree of epithelial surface damage. Results revealed a significant reduction in microprojection density, microprojection height, and depth of the epithelial surface with increasing time and phonation magnitudes doses, signifying increased epithelial surface damage risk with excessive and prolonged vibration exposure. Destruction to the epithelial cell surface may provide significant insight into the disruption of cell function following prolonged vibration exposure. One important goal achieved in the present study was the quantification of epithelial surface damage using objective imaging criteria. These data provide an important foundation for future studies of long-term tissue recovery from excessive and prolonged vibration exposure.

Effects of phonation time and magnitude dose on vocal fold epithelial genes, barrier integrity, and function.

To investigate the effects of increasing time and magnitude doses of vibration exposure on transcription of the vocal folds junctional proteins, structural alterations, and functional tissue outcomes.

Acute exposure to vibration is an apoptosis‐inducing stimulus in the vocal fold epithelium

Clinical voice disorders pose significant communication-related challenges to patients. The purpose of this study was to quantify the rate of apoptosis and tumor necrosis factor-alpha (TNF-α) signaling in vocal fold epithelial cells in response to increasing time-doses and cycle-doses of vibration. 20 New Zealand white breeder rabbits were randomized to three groups of time-doses of vibration exposure (30, 60, 120min) or a control group (120min of vocal fold adduction and abduction). Estimated cycle-doses of vocal fold vibration were extrapolated based on mean fundamental frequency. Laryngeal tissue specimens were evaluated for apoptosis and gene transcript and protein levels of TNF-α. Results revealed that terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was significantly higher after 120min of vibration compared to the control. Transmission electron microscopy (TEM) revealed no significant effect of time-dose on the mean area of epithelial cell nuclei. Extrapolated cycle-doses of vibration exposure were closely related to experimental time-dose conditions, although no significant correlations were observed with TUNEL staining or mean area of epithelial cell nuclei. TUNEL staining was positively correlated with TNF-α protein expression. Our findings suggest that apoptosis can be induced in the vocal fold epithelium after 120min of modal intensity phonation. In contrast, shorter durations of vibration exposure do not result in apoptosis signaling. However, morphological features of apoptosis are not observed using TEM. Future studies are necessary to examine the contribution of abnormal apoptosis to vocal fold diseases.

Nonstimulated rabbit phonation model: Cricothyroid approximation

To describe a nonstimulated in vivo rabbit phonation model using an Isshiki type IV thyroplasty and uninterrupted humidified glottal airflow to produce sustained audible phonation.

Evaluation of Dying Vocal Fold Epithelial Cells by Ultrastructural Features and TUNEL Method.

Cell death is a regulated mechanism of eliminating cells to maintain tissue homeostasis. This study described 2 methodological procedures for evaluating cell death in the epithelium of immobilized, approximated and vibrated vocal folds from 12 New Zealand white breeder rabbits. The gold standard technique of transmission electron microscopy evaluated high-quality ultrastructural criteria of cell death and a common immunohistochemical marker, the terminal deoxynucleotidyl transferase dUTP nick end labeling method, to confirm cell death signaling. Results revealed that ultrastructural characteristics of apoptotic cell death, specifically condensed chromatin and apoptotic bodies, were observed after vocal fold vibration and approximation. Although episodes of necrosis were rare, few enlarged cell nuclei were present after vibration and approximation. The vocal fold expresses an immunohistochemical marker for apoptosis along the apical surface of the epithelium. This study provides a solid foundation for future investigations regarding the role of cell death in vocal fold health and disease.

Apoptosis and Vocal Fold Disease: Clinically Relevant Implications of Epithelial Cell Death.

Purpose Vocal fold diseases affecting the epithelium have a detrimental impact on vocal function. This review article provides an overview of apoptosis, the most commonly studied type of programmed cell death. Because apoptosis can damage epithelial cells, this article examines the implications of apoptosis on diseases affecting the vocal fold cover. Method A review of the extant literature was performed. We summarized the topics of epithelial tissue properties and apoptotic cell death, described what is currently understood about apoptosis in the vocal fold, and proposed several possible explanations for how the role of abnormal apoptosis during wound healing may be involved in vocal pathology. Results and Conclusions Apoptosis plays an important role in maintaining normal epithelial tissue function. The biological mechanisms responsible for vocal fold diseases of epithelial origin are only beginning to emerge. This article discusses speculations to explain the potential role of deficient versus excessive rates of apoptosis and how disorganized apoptosis may contribute to the development of common diseases of the vocal folds.

Randomized controlled trial of supplemental augmentative and alternative communication versus voice rest alone after phonomicrosurgery

Objective This randomized trial investigated voice rest and supplemental text-to-speech communication versus voice rest alone on visual analog scale measures of communication effectiveness and magnitude of voice use. Study Design Randomized clinical trial. Setting Multicenter outpatient voice clinics. Subjects Thirty-seven patients undergoing phonomicrosurgery. Methods Patients undergoing phonomicrosurgery were randomized to voice rest and supplemental text-to-speech communication or voice rest alone. The primary outcome measure was the impact of voice rest on ability to communicate effectively over a 7-day period. Pre- and postoperative magnitude of voice use was also measured as an observational outcome. Results Patients randomized to voice rest and supplemental text-to-speech communication reported higher median communication effectiveness on each postoperative day compared to those randomized to voice rest alone, with significantly higher median communication effectiveness on postoperative days 3 (P = .03) and 5 (P = .01). Magnitude of voice use did not differ on any preoperative (P > .05) or postoperative day (P > .05), nor did patients significantly decrease voice use as the surgery date approached (P > .05). However, there was a significant reduction in median voice use pre- to postoperatively across patients (P < .001) with median voice use ranging from 0 to 3 throughout the postoperative week. Conclusion Supplemental text-to-speech communication increased patient-perceived communication effectiveness on postoperative days 3 and 5 over voice rest alone. With the prevalence of smartphones and the widespread use of text messaging, supplemental text-to-speech communication may provide an accessible and cost-effective communication option for patients on vocal restrictions.

Recovery of Vocal Fold Epithelium after Acute Phonotrauma

We investigated the timeline of tissue repair of vocal fold epithelium after acute vibration exposure using an in vivo rabbit model. Sixty-five New Zealand white breeder rabbits were randomized to 120 min of modal- or raised-intensity phonation. After the larynges were harvested at 0, 4, 8, and 24 h, and at 3 and 7 days, the vocal fold tissue was evaluated using electron microscopy and quantitative real-time polymerase chain reaction. There was an immediate decrease in the microprojection depth and height following raised-intensity phonation, paired with upregulation of cyclooxygenase-2. This initial 24-h period was also characterized by the significant downregulation of junction proteins. Interleukin 1β and transforming growth factor β1 were upregulated for 3 and 7 days, respectively, followed by an increase in epithelial cell surface depth at 3 and 7 days. These data appear to demonstrate a shift from inflammatory response to the initiation of a restorative process in the vocal fold epithelium between 24 h and 3 days. Despite the initial damage from raised-intensity phonation, the vocal fold epithelium demonstrates a remarkable capacity for the expeditious recovery of structural changes from transient episodes of acute phonotrauma. While structurally intact, the return of functional barrier integrity may be delayed by repeated episodes of phonotrauma and may also play an important role in the pathophysiology of vocal fold lesions.

Subject-Specific Computational Modeling of Evoked Rabbit Phonation

When developing high-fidelity computational model of vocal fold vibration for voice production of individuals, one would run into typical issues of unknown model parameters and model validation of individual-specific characteristics of phonation. In the current study, the evoked rabbit phonation is adopted to explore some of these issues. In particular, the mechanical properties of the rabbits vocal fold tissue are unknown for individual subjects. In the model, we couple a 3D vocal fold model that is based on the magnetic resonance (MR) scan of the rabbit larynx and a simple one-dimensional (1D) model for the glottal airflow to perform fast simulations of the vocal fold dynamics. This hybrid three-dimensional (3D)/1D model is then used along with the experimental measurement of each individual subject for determination of the vocal fold properties. The vibration frequency and deformation amplitude from the final model are matched reasonably well for individual subjects. The modeling and validation approaches adopted here could be useful for future development of subject-specific computational models of vocal fold vibration.