Vocal fatigue is a common complaint among professional voice users including teachers, significantly affecting their job performance and quality of life (Moreno et al., 2025). Vocal fatigue is typically assessed based on subjective questionnaires. Research revealed strong links between vocal fatigue and respiratory functions (Tong & Sataloff, 2022), as well as aerodynamic measures (e.g., Fujiki & Sivasankar et al., 2021), yet no standardized, quantifiable assessment protocol exists (Nanjundeswaran et al., 2024; Moreno et al., 2025). This study aimed to establish clinical indications and diagnostic criteria for using airflow measures in individuals with vocal fatigue.
Ten teachers with vocal fatigue (5 males, 5 females) and ten healthy controls were recruited, and they underwent stroboscopic screening and baseline assessments including self-reported measures using Vocal Fatigue Index (VFI), Voice Handicap Index (VHI-10), and Borg CR10 scale, and objective assessments of pulmonary and phonatory functions. Pulmonary measures included forced vital capacity (FVC), forced expiratory volume in one second (FEV1), peak expiratory flow (PEF), FEV1/FVC ratio, and maximum expiratory/inspiratory pressure (MEP/MIP). Phonatory measures included phonation threshold pressure (PTP), maximum phonation time (MPT), mean fundamental frequency (F0), F0 range, relative fundamental frequency (RFF), sound pressure level (SPL), cepstral peak prominence (CPP), S/Z ratio, and harmonic-to-noise ratio (HNR), measured from sustained vowel and continuous speech. Following a 20-minute phonation task involving sustained vowel production, all parameters were reevaluated.
Linear mixed-effects models revealed a significant Time × Group interaction for self-reported fatigue, airflow, and voice measures, with greater post-task changes in the fatigue group. In this group, FEV1, PEF, MEP/MIP, and MPT decreased significantly from pre- to post-task, while PTP and F0 increased. Changes in controls were minimal. Baseline differences were small but became more apparent after the task. This pilot study shows that pulmonary and phonatory measures are sensitive to short-term vocal fatigue. Those more susceptible showed greater physiological changes, with effect sizes suggesting clinical relevance. Receiver Operating Characteristic (ROC) curve analysis was performed on pre- and post-task changes across all parameters as an exploratory analysis, with Area Under the Curve (AUC) calculated. Preliminary findings indicate these measures may have discriminative ability.