The purpose of this thesis is to examine the effects of inhaled corticosteroid drugs (ICs) on the voice due to their frequent use in treating an increasing prevalence of asthma disorders. As part of a larger five-year study, the focus of this thesis is specifically on whether 8 weeks of in vivo exposure to ICs will cause changes in the sustained subglottal pressure, sustained airflow, and visual-perceptual ratings of edema and erythema in excised rabbit larynges. Researchers administered either ICs or a control nebulized isotonic saline solution to 22 rabbits in vivo, sacrificed them, and harvested their larynges for benchtop research. While ensuring proper tissue preservation, researchers then finely dissected the larynges to expose the true vocal folds and run phonation trials. Dependent variables included continuous acoustic signals (Hz), subglottal pressure (cm H2O), and airflow (L/min) data for 15 phonation trials per rabbit larynx. Researchers also collected still image photographs at this time and subsequently normalized them for use in the visual-perceptual portion of this thesis. For visual-perceptual ratings, raters used a 0-3 equal appearing interval scale to rate aspects of edema and erythema on left and right vocal fold and arytenoid tissues. Results indicate that, when compared to control larynges exposed to nebulized isotonic saline, experimental larynges treated with ICs require significantly higher subglottal pressure to maintain phonation, p < .05. Mean sustained phonation for experimental larynges is 11.24 cm H2O compared to 8.92 cm H2O for that of control larynges. Phonation trials for experimental larynges have significantly higher sustained airflow with a mean of 0.09 L/min compared to 0.07 L/min for that of control larynges, p < .05. Surprisingly, experimental larynges have higher average fundamental frequencies with less variability (mean: 519 Hz, standard deviation: 66 Hz) than that of control larynges (mean: 446 Hz, standard deviation: 130 Hz). On visual-perceptual ratings, experimental larynges have significantly higher severity ratings on all eight items rated, p < .0001 - p = .0305. Based on these results, it is concluded that ICs cause significant damage to rabbit vocal folds, as evidenced by higher sustained pressure, higher airflow, and higher severity ratings for experimental versus control larynges. The dependent variables in this thesis are novel in benchtop model research and demonstrate a unique perspective on this research question. Thus, this thesis informs future phonation, benchtop, and visual-perceptual research.

The purpose of this thesis is to investigate the reversibility of the adverse effects of combination inhaled corticosteroids (ICs) on vocal fold health as part of a five-year study. This pilot study tested the hypothesis that the adverse effects of ICs may be induced and then reversed, using a benchtop model and rabbit larynges measuring sustained subglottic pressure and airflow. Eighteen rabbits were assigned randomly to 5 subgroups, including baseline, induction experimental, induction control, reversibility experimental, and reversibility control. Baseline rabbits did not receive any treatment. Both experimental groups, induction and reversibility, were administered Advair until visual-perceptual ratings were noted. Their paired control groups were administered nebulized saline in the same dosage levels. Induction groups were immediately sacrificed, while reversibility groups entered a withdrawal phase until visual-perceptual ratings showed a return to baseline. Larynges were dissected and mounted on a benchtop model for phonation trials. Dependent variables included sustained phonatory pressure (cm/H2O) and sustained phonatory airflow (L/min). The results of phonation trials indicate that sustained pressure and flow were higher for both induction and reversibility experimental groups when compared to baseline and control groups. The reversibility experimental group had lower sustained pressure and flow than the induction experimental group. These results indicate a reduction of signs after a period of rest. These findings suggest that voice symptoms may be reversible to a degree after combination IC use. These are important preliminary data that support future studies with larger sample sizes to confirm findings.

La collision entre les plis vocaux lors de la phonation, phénomène physiologique essentiel pour la synchronisation de la vibration des plis, est également une composante du phonotraumatisme. Le rôle du phonotraumatisme dans la physiopathologie des dysphonies est communément admis mais sa nature reste mal définie et sa quantification difficile. Ce travail propose d’aborder cette question au moyen d’approches in vivo sur des sujets sains et ex vivo sur des larynx humains excisés. L’objet de ce travail est l’étude du comportement laryngé lorsque le larynx est soumis à des conditions de pression sous-glottique extrêmement élevées. In vivo, l’étude de la voix criée reposait sur la mesure constante de la pression sous-glottique. Ex vivo, cette dernière était manipulée en dehors de toute modification des autres paramètres de contrôle. Le volet ex vivo a nécessité un développement méthodologique (modernisation et adaptation au larynx humain) du banc expérimental utilisé pour des larynx animaux. Les résultats ont montré l’existence chez les locuteurs sains d’un « plafonnement » dans l’intensité vocale et le signal électroglottographique pour les très hauts niveaux de pression sous-glottique. Les études sur larynx humains excisés mesuraient la force de collision entre les plis vocaux sous l’effet de la pression sous-glottique et ont mis en évidence l’existence, ici aussi, d’un « plafonnement » de cette force lorsque la pression sous-glottique est très élevée. Les observations rapportées par ce travail ont un intérêt clinique important même si les phénomènes physiques sous-jacents restent à préciser. / The collision between the vocal folds during phonation is a physiological phenomenon with a powerful role in the synchronization of their vibration. This collision is also a component of the phonotrauma. The role of phonotrauma in the pathophysiology of dysphonia is commonly accepted but its nature still unclear and its quantification remains difficult. This work proposes, an in vivo study in healthy subjects, and an ex vivo one on excised human larynges. The purpose of this work was to study of the laryngeal behavior when the larynx is subjected to extremely high subglottic pressure. In vivo, it is studying the shouted voice with constant measure of subglottal pressure. Ex vivo, the subglottic pressure is directly manipulated. The ex vivo study required a methodological development to modernize the experimental bench used for animal larynges studies and to adapt it to the human larynx. The results showed, in healthy speakers the existence of a "plateau" in the vocal intensity and in the electroglottographic signal for very high levels of subglottic pressure. The excised larynx studies measured the collision force between the vocal folds and its changes depending on other acoustic and electroglottographic parameters. They highlighted the existence, here too, of a "plateau" in the level of the collision force when the subglottic pressure was very high. The observations presented in this work are, to our knowledge, unprecedented. They have important clinical interest for understanding the concept of phonotrauma. Their interpretation in physical terms remains very incomplete.