Respiratory Responses to Vocal Demand Tasks: A Scoping Review

Objective: This study aims to identify sensitive respiratory, laryngeal, and self-perceptual measures for assessing vocal fatigue and to determine tasks that effectively elicit the experience of vocal fatigue. Methods: A scoping review was conducted using Cochrane, Medscape, PubMed, and Google Scholar databases. A total of 17 studies met the inclusion criteria and were reviewed in full and summarized. The studies were analyzed to extract relevant data on respiratory, laryngeal, and self-perceptual measures used to assess vocal fatigue, as well as the tasks employed to elicit vocal fatigue. Results: Of the 17 articles, 14 studies involved vocally healthy individuals, while three studies included participants with vocal fatigue. Phonation threshold pressure (PTP) was the most used and most consistent indirect respiratory measure in detecting vocal fatigue; however, only five studies included direct measurements of respiratory patterns and only two included ventilatory data. Laryngeal measures demonstrated inconsistent response to a vocal demand task, except mean fundamental frequency among vocally healthy participants, but not in those with complaints of vocal fatigue. Short-duration vowel tasks were found to be capable of eliciting vocal fatigue similar to prolonged reading tasks. Conclusion: Phonation threshold pressure (PTP) consistently captured vocal fatigue and can serve as an indirect respiratory measure. Measures of respiratory patterning and ventilation require further study. Fundamental frequency shows potential as a laryngeal measure of vocal fatigue in vocally healthy individuals but requires further investigation in those with vocal fatigue. Short-duration tasks elicit vocal fatigue and need to be investigated in future study protocols. These findings highlight the need to develop systematic protocols for ongoing assessment and monitoring of vocal fatigue to enhance both clinical practice and research methodologies.