Efeitos da Fotobiomodulação com Laser de Baixa Potência na Laringe em mulheres: análise por meio da Videolaringoscopia de Alta Velocidade

Abstract

Introduction: Photobiomodulation has become widespread in vocal clinical practice as one of the adjunct options to traditional vocal therapy. Despite its widespread use, little is known about its interactions with laryngeal structures and phonation. Cellular studies and research from other subfields have shown that the use of low-level laser (LLL) is associated with anti-inflammatory effects, improved healing and recovery from tissue fatigue, and improved cellular performance through increased ATP production. Studies are needed to standardize photobiomodulation for clinical voice professionals and dysphonic patients, guiding its application site and dosage in therapy, and verifying whether there actually are positive changes in phonation physiology to justify its use. Objectives: To investigate the application of low-level laser in the larynx, establishing specific points in the cervical topography for its application, evaluating the incidence of light according to skin phototype and body mass index (BMI); and to analyze its immediate effect, associated with the voiced tongue trill technique, on the glottic function of women with behavioral dysphonia, through the analysis of digital videokymography parameters obtained by high-speed videolaryngoscopy. Methods: This research project was approved by the Ethics Committee of the Federal University of Minas Gerais (UFMG) (approval number 4,704,038). Two subprojects were designed to complete the final thesis, resulting in two studies. The first subproject, a cross-sectional, analytical, observational study, served as guidance for the next stage and was titled, "Photobiomodulation in the larynx: Application sites and influence of skin phototype and body mass index." Fifteen vocally healthy women, aged 18 to 50, participated in the study. They were organized into three groups based on body mass index (BMI) and skin phototype, using the Fitzpatrick protocol. Six anatomical landmarks were defined to locate the larynx and its intrinsic muscles, targeting the thyroarytenoid, lateral cricoarytenoid, and cricothyroid muscles. Visual monitoring was performed by videonasolaryngoscopy to assess the presence or absence of light and the illumination level (ranging from very weak to very strong) in the laryngeal region during laser application at doses of 3 J, 6 J, and 9 J. Visual analysis was performed by consensus between two researchers and involved the use of a flexible endoscope to examine the images obtained and verify the correspondence between the light emitted by the laser device in contact with the skin of the cervical region and the image obtained by flexible videolaryngoscopy, as well as the influence of BMI and skin phototype on the intensity of the visualized illumination. The second subproject is an experimental, randomized clinical trial to evaluate the efficacy of the therapy applied to a population with a specific clinical condition, entitled, “Evaluation of the effect of photobiomodulation with low level light laser using videokymography in women with behavioral dysphonia." Thirty women with behavioral dysphonia and abnormal laryngeal examination, in addition to a body mass index (BMI) below 30, were divided into two groups. High-speed videolaryngoscopy was performed before and after laser application at predefined points from the previous subproject. The first group, called the placebo group, underwent laser application without the use of light combined with the voiced tongue trill technique (VTTT) for 5 minutes. The second group, called the experimental group, underwent 9 J photobiomodulation at points corresponding to the intrinsic muscles of the larynx and underwent VTTT for 5 minutes. Results: In Subproject 1, laser light reached the larynx at 3 J, 6 J, and 9 J, specifically at the anterior commissure of the larynx, their membranous portion (thyroarytenoid muscle), cartilaginous portion, and the cricothyroid muscle. Light intensity decreased in overweight and obese participants and increased in those with Fitzpatrick skin types IV and V. In Subproject 2, it was not possible to determine whether 9 J photobiomodulation alone, when combined with VTTT, significantly modified the videokymographic parameters. Despite careful diagnostic matching of laryngeal changes between the control and experimental groups, pre-intervention analysis revealed statistically significant differences in maximum and average glottal opening and the videokymographic index at the middle third of the vocal folds. However, within the experimental group, an increase in average glottal opening in the anterior third was observed after the laser and VTTT intervention. Conclusion: The results indicate that photobiomodulation therapy should be individualized, considering each person's characteristics. It was found that low-level laser penetration differs according to skin phototype and BMI, being more evident in individuals with Fitzpatrick phototypes IV and V and less evident in higher BMIs. The evidence that laser light reaches the larynx at specific anatomy may guide the standardization of application points in vocal practice. Furthermore, the changes caused by low-level laser application suggest that phonatory physiology changes when the VTTT is used in combination with the 9 J laser at points corresponding to the intrinsic laryngeal muscles, with a possible increase in their contraction strength. Further studies should evaluate photobiomodulation in the larynx, selecting more uniform samples or with a larger population to investigate the effects of PBM on vocal physiology.