This thesis is part of a larger series of studies being conducted by Kristine Tanner, PhD, Associate Professor in the Department of Communication Disorders at Brigham Young University (BYU). The larger project is funded by the National Institute on Deafness and Other Communication Disorders at the National Institutes of Health. This thesis primarily investigated the effects of combination inhaled corticosteroids (ICs) on aerodynamic measures of the voice. In recent years, an increase in the localized laryngeal side effects from IC treatment, including dysphonia, have been reported. This study employed a between-groups experimental design, with two groups of rabbit larynges having been exposed to either ICs or nebulized isotonic saline two times each day for eight weeks at The University of Utah. For this study, the independent variable is group condition (i.e., IC versus saline) and the dependent variables are two aerodynamic measurements made at the onset of phonation using a benchtop experimental setup, namely phonation threshold pressure (PTP; cmH2O) and phonation threshold flow (PTF; L/min). The results of this study indicate a significant difference in PTP and PTF between vocal folds treated with IC as compared to vocal folds treated with nebulized isotonic saline solution. Implications of this study suggest negative changes in the voice due to IC treatment.

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 The other experimental group (i.e., the reversibility group) had ICs withdrawn once visible changes were detected via endoscopy; larynges were harvested only after these changes no longer differed from baseline.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.