The Effect of Laryngeal Dehydration and Nebulized Osmotic Agents on the Voice.

Objective: This study investigates the effects of dehydration induced by dry air breathing and the nebulization of various osmotic agents on vocal parameters, including perceptual, acoustic, and electroglottographic measures.

Methods: Thirty normophonic females (age x̅ = 26, SD = 1.67) participated over three consecutive days. On the first day, the baseline data were meticulously collected before the participants underwent a 22-minute session of transoral dry air breathing. Immediately after this desiccation protocol, measurements were taken to establish the initial effects. Subsequently, one of three osmotic agents was randomly selected for each participant. These agents included hypotonic distilled water, 0.9% isotonic saline, and 3% hypertonic saline. Each participant then underwent a 10-minute nebulization session with 5 mL of the assigned osmotic agent. The process was repeated on the second and third days. Each day, the participants again experienced the 22-minute transoral dry air breathing session. The evaluations were performed by Borg CR-10 (perceived vocal effort), electroglottography (EGG), voice onset time (VOT), nasalance score (NS), and cepstral peak prominence analyses with CAPE-V sentences (s).

Results: No statistically significant differences were found in the EGG parameters between the preliminary recordings, post transoral medical-grade dry air protocol, and after each of task-hypotonic, task-isotonic, and task-hypertonic. Following the transoral medical-grade dry air protocol, both /s1/-CPP and /s5/-CPP values decreased compared with the preliminary recordings. Only /s1/-CPP values increased after the 0.9% isotonic saline nebulization. NS from preliminary measurements was higher for both oronasal and nasal texts compared with scores after the dry air protocol and nebulization. Voiceless plosive VOT values decreased solely after the 0.9% isotonic saline nebulization. Participants' Borg CR-10 scores increased after transoral medical-grade dry air protocol and decreased after nebulization with distilled water and 0.9% isotonic saline.

Conclusions: Isotonic saline and distilled water nebulization protocols demonstrated a trend toward mitigating the adverse effects of the transoral medical-grade dry air inhalation protocol on vocal parameters.