Acoustic and Multiparametric Measurements After Photobiomodulation (PBM) in Women Without Self-Reported Voice Complaints: Is There Any Difference?

PURPOSE: To describe and analyze the effects of photobiomodulation on the acoustic and multiparametric indices of women without self-reported voice complaints. METHODS: Experimental and randomized study (Consolidated Standards of Reporting Trials -CONSORT - and ReBEC RBR-9gh9ht7). The participants (18-45 years old) were randomly divided into two groups: the experimental group (EG), receiving 9 J of infrared wavelength (808-1100 nm) at three equidistant points from each other (the laryngeal prominence and the right and left hemifaces of the thyroid cartilage) and the placebo group (PG): placebo laser application (inactive light). A sociodemographic questionnaire and the Vocal Fatigue Index were administered before beginning. Voice samples were recorded before and after each intervention (sustained /a/ vowel, connected speech, and Consensus Auditory-Perceptual Evaluation of Voice sentences). Acoustic analysis focused on the following multiparametric acoustic indices: Acoustic Voice Quality Index [AVQI], Acoustic Breathiness Index [ABI], Smoothed Cepstral Peak Prominence [CPPS] (Praat software), and Cepstral Peak Prominence [CPP] (VoxMetria - CTS Informática). Fisher's exact test was used for intergroup comparisons of nominal variables, with posthoc pairwise comparisons using the Z test. A General Linear Model was also applied, in which the significance of fixed effects was assessed using F tests, and a Linear Mixed Model with posthoc analysis was conducted using the t test. All analyses adopted a significance cutoff of 0.05. RESULTS: Twenty-eight women without self-reported voice complaints participated in this study, with PG (n = 14) having a mean age of 26.93 years (standard deviation [SD] = 6.50) and EG (n = 14) having a mean age of 26.64 years (SD = 5.96). Among the multiparametric measurements analyzed, only CPPS showed a significant difference, though this was close to the statistical threshold (P = 0.048) in the Moment vs. Group interaction. CONCLUSION: For this sample, no significant differences were found for AVQI, ABI, or CPP. Although CPPS showed a significant change for the EG, this change was small and therefore not sufficient to suggest clinical applicability at this moment.