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.

Although combination inhaled corticosteroids (ICs) are known to cause voice disorders in otherwise vocally healthy individuals, it is unknown whether those adverse effects can be reversed by the cessation of treatment. Quantitative aerodynamic measures such as phonation threshold pressure (PTP) and phonation threshold flow (PTF) can be used to identify the development of, and recovery from, vocal pathologies. We examined the effects and reversibility of ICs on laryngeal aerodynamics. This study was a mid-project investigation as part of a larger ongoing project. The 18 larynges were from rabbits that received ICs, a control condition, or no treatment. Experimental group rabbits received ICs twice per day until inflammatory changes (e.g., erythema, edema) became visible through endoscopic observation. One experimental group (i.e., the induction group) received treatment until symptoms were observed and then larynges were harvested. The other experimental group (i.e., the reversibility group) had ICs withdrawn once visible changes were detected via endoscopy; larynges were harvested only after these changes no longer differed from baseline. Both experimental groups had corresponding control rabbits that received twice-daily nebulized saline and followed the same withdrawal and larynx harvest schedule. A final group received no treatment. During benchtop phonation trials, PTP and PTF values were determined. All data were analyzed using descriptive and parametric statistics. No significant between-group differences were observed. Descriptively, however, average PTP and PTF values for the reversibility group were lower than the induction group. Additionally, average PTP and PTF values for the reversibility group were slightly lower than the induction group. Both experimental groups had higher PTP and PTF values than the control larynges. The results of this study indicate a trend in recovery for larynges afforded a recovery period from ICs. Further testing is needed to substantiate these preliminary findings.