Protective Strategies Against Dysphonia in Teachers: Preliminary Results Comparing Voice Amplification and 0.9% NaCl Nebulization

Abstract

This study aimed to compare the effects of two protective strategies, voice amplification (VA) and 0.9% NaCl nebulization (NEB), on teachers' voice in the work setting. An interventional evaluator-blind study was conducted, assigning 53 teachers from two public high schools to one of the two protective strategy groups (VA or NEB). Vocal function was assessed in a sound-treated booth before and after a 4-week period. Assessment included the severity of voice impairment (Consensus Auditory-Perceptual Evaluation of Voice [CAPE-V]), acoustic analysis of fundamental frequency (f0), sound pressure level (SPL), jitter, shimmer, glottal-to-noise excitation ratio (GNE), noise (VoxMetria), and the self-rated Screening Index for Voice Disorder (SIVD). Data were statistically analyzed using SPSS Statistics (version 22) with a significance level of P ≤ 0.05. Effect size was calculated using Cohen's d coefficient. There were no statistical differences between groups at baseline in terms of age, sex, time of teaching, teaching workload, and voice outcomes, except for SPL. During postintervention between groups, NEB displayed lower SIVD scores (VA = 3; NEB = 0; P = 0.018) and VA had lower acoustic irregularity (VA = 3.19; NEB = 3.69; P = 0.027), with moderate to large effect size. Postintervention within-groups decreased CAPE-V for VA (pretest = 31.97; posttest = 28.24; P = 0.021) and SIVD for NEB (pretest = 3; posttest = 0; P = 0.001). SPL decreased in both groups, NEB decreased in men only, and VA decreased in both men and women. NEB increased f0 for female participants (P ≤ 0.001). Both VA and NEB may help mitigate dysphonia in different pathways, being potential interventions for protecting teachers' voices in the work setting. An ongoing study with a control group will further support these preliminary results.