Pulmonary Function, Functional Capacity, Voice, and Sleep in Post-COVID-19 Individuals With and Without Inspiratory Muscle Weakness

OBJECTIVE: To compare pulmonary function, functional capacity, voice, and sleep in post-COVID-19 individuals with and without inspiratory muscle weakness, as well as to investigate the association between vocal deviations, respiratory muscle strength, pulmonary function, functional capacity, and sleep parameters. METHODS: Cross-sectional study with 28 post-COVID-19 adults, distributed into groups with (n = 14) and without (n = 14) inspiratory muscle weakness (maximal inspiratory pressure -MIP-<70% of the predicted value). Pulmonary function was assessed by spirometry; respiratory muscle strength by maximal respiratory pressures; inspiratory muscle endurance with a load of 60% of MIP; functional capacity by the Six-Minute Walk Test; and fatigue by the Fatigue Severity Scale and Chalder Fatigue Scale; voice was assessed using the Vocal Handicap Index (VHI), Vocal Fatigue Index (VFI), and Maximum Phonation Time (MPT); and sleep was assessed using the Insomnia Severity Index, Epworth Sleepiness Scale, and nocturnal oximetry. RESULTS: Individuals with inspiratory muscle weakness presented a higher prevalence of fatigue (P = 0.02), higher scores in the physical domain (P = 0.008) and in the total VHI score (P = 0.01), greater occurrence of vocal functional impact (functional domain of the VHI) when analyzed in a categorized way (P = 0.02), higher scores in the VFI (factor one P = 0.008; factor two P = 0.002; factor three P = 0.002; total score P = 0.03), and lower MPT of the phonemes /s/ and /z/ (P = 0.02; P = 0.03) when analyzing continuous and categorical variables. A negative correlation was observed between the total VFI score and MIP (r = -0.467; P = 0.01), as well as between the VFI and the percentage of predicted MIP (r = -0.396; P = 0.03), indicating that lower levels of inspiratory muscle strength were associated with greater vocal fatigue. CONCLUSION: Inspiratory muscle weakness in post-COVID-19 individuals is associated with greater fatigue and poorer vocal outcomes, underscoring the importance of respiratory assessment in understanding the interaction between breathing and voice.