Efeitos imediatos da fotobiomodulação com laser de baixa potência em mulheres sem alteração vocal e em mulheres disfônicas

Abstract

Introduction: Adjuvant resources has been increasingly used in speech-language-hearing clinical practice to enhance therapeutic gains. Among other approaches, photobiomodulation (PBM) therapy with low-level LASER (LLL) is an advancing treatment alternative in speech-language-hearing therapy and has been used as an ergogenic resource to improve performance and delay muscle fatigue in different exercise modes. PBM therapy applies light to a biological system to induce a photochemical process, which can increase cell metabolism. Despite its wide use in voice clinics, there is no robust evidence of its effects as a therapeutic technique, considering clinical protocol aspects such as dosimetric parameters, irradiated area, and time-response factor. Since the selection of irradiation parameters often pose a dilemma, the search for standardization is desirable for better clinical guidance. Objectives: To conduct a literature review on the PBM therapeutic effects applicable to speech-language-hearing therapy and analyze the safety and immediate effects of applying LLL in vocally healthy women and those with behavioral dysphonia. Methods: This randomized experimental study was approved by the Ethics Committee of the Federal University of Minas Gerais (UFMG) (evaluation report no. 4,704,038). Three studies were designed to structure the thesis: an integrative literature review and two experimental, double-blind, placebo-controlled studies. Study 1, entitled “Immediate effects of photobiomodulation in speech-language-hearing clinical practice: An integrative literature review”, searched the literature on PBM therapeutic effects applicable to speech-language-hearing practice. It included original articles whose full texts were available, published between 2010 and 2020, assessing the PBM therapeutic effects in situations applicable to the various areas of speech-language-hearing practice. The full texts were read and analyzed considering their year and place of publication, language, first author’s academic degree, study design, classification of the level of scientific evidence, objectives, sample, PBM therapy types, wavelength, number of sessions, application areas, energy per point, application time, and outcomes regarding each topic. Altogether, 23 references were selected – 10 national and 13 international articles. Study 2 (phase 1 of the research) had an experimental design and was entitled “Immediate effects of photobiomodulation with low-level LASER in women without vocal or laryngeal changes: Preliminary results”. Its sample included 36 women without vocal/laryngeal changes, who were submitted to an exercise protocol associated with low-power LASER in a single session to analyze their immediate effect in different treatment groups. After randomization and allocation, participants were distributed into four groups: group 1, submitted to simulated treatment with the device turned off (placebo LASER applied to seven points for 60 seconds immediately before performing the voiced tongue trill technique for 3 minutes). In group 2, the experiment was carried out in the same way, but with infrared LLL applied at 3 joules per point (totaling 21 joules). In group 3, it was irradiated at 6 joules per point in the infrared wavelength range for 60 seconds (totaling 42 joules). Lastly, it was irradiated at 9 joules in group 4, likewise in the infrared spectrum, for 90 seconds at each point (totaling 63 joules). The experimental groups received therapeutic light immediately before the vocal technique at seven specific anatomical points on the neck (in both hemilarynges) to reach the topography of the anterior commissure of the larynx and the thyroarytenoid, lateral cricoarytenoid, and cricothyroid muscles. After irradiation, participants performed the voiced tongue trill technique for 3 minutes. The auditory-perceptual evaluation of voice, acoustic analysis, and self-perceived phonatory effort, measured before and immediately after intervention, were the outcome variables. Five experienced speech-language-hearing pathologists, blinded to the intervention and moment of assessment, conducted the comparative auditory-perceptual evaluation in pairs. The following parameters were selected for the acoustic analysis: jitter, period perturbation quotient (PPQ), shimmer, amplitude perturbation quotient (APQ), noise-to-harmonic ratio (NHR), vowel /a/ maximum phonation time (MPT), and vowel /a/ and linked speech cepstral peak prominence (CPP) and cepstral peak prominence-smoothed (CPPS). The self-perceived phonatory effort was analyzed with the CR10-BR Borg Scale after the procedures, when participants answered on a Likert-type scale, ranging from “0: no vocal effort” to “10: maximum effort”. Study 3 (phase 2), entitled “Immediate effects of photobiomodulation with low-level LASER in women with vocal and laryngeal changes”, comprised 30 women diagnosed with behavioral dysphonia secondary to glottal gaps or benign vocal fold lesions, randomized into two groups: placebo group (using the equipment without energy emission followed by the voice tongue trill technique for 5 minutes); and experimental group, in which the infrared LASER was applied at 9 joules (totaling 63 joules) for 90 seconds at seven points on the neck, according to the protocol established in phase 1 of the research, followed by the voice tongue trill technique for 5 minutes. Voices were recorded before and immediately after procedures and submitted to auditory-perceptual evaluation and acoustic analysis. Four experienced speech-language-hearing therapists performed the auditory-perceptual evaluation of voice with a numerical scale. The acoustic analysis addressed the jitter, PPQ, shimmer, APQ, NHR, MPT, and CPPS of linked speech and sustained vowel and extracted the multiparametric index (AVQI). The self-perceived phonatory effort was analyzed with the CR10-BR Borg Scale. Four otorhinolaryngologists independently evaluated the laryngeal images by comparing them in pairs. Results: The results of study 1 demonstrated that Brazil is the leader in publications. There is a large concentration of studies focused on oral motor therapy, and their first authors mostly had a physical therapy, medical, or dental degree. The results of study 2 indicated that the infrared LASER at 9 joules per point before exercise improved acoustic measures of shimmer and APQ in normophonic women. Furthermore, there was no significant sensation of worsened voice production. In study 3, the findings demonstrated increased vowel MPT and CPPS, decreased phonatory effort, and improved vocal fold vibration parameters. Conclusions: The results suggest that photobiomodulation brings benefits in different disorders treated by speech-language-hearing pathologists. However, given the methodological diversity, the data in the literature are controversial, and the evidence is questionable. The energy of 9 J (total of 63 joules) in the larynx may be a therapeutic window to be recommended in voice clinical practice in light-skinned women without vocal or laryngeal disorders, with normal body mass index. Moreover, these are promising dosimetric parameters with a possible enhancing effect on vocal results in the treatment of dysphonic women.