Efeitos agudos de diferentes posicionamentos sobre as medidas de pressões respiratórias e ativação eletromiográfica dos músculos respiratórios em indivíduos com Distrofia Muscular de Duchenne e em indivíduos saudáveis

Abstract

Introduction: The influence of body position on ventilation has been studied for decades in both healthy individuals and patients with various respiratory conditions. The neuromuscular system's ability to generate force is influenced by multiple factors, and postural changes have the potential to alter the length and position of respiratory muscles, thereby affecting their function and ability to generate tension and force. In Duchenne Muscular Dystrophy (DMD), disease progression leads to structural, anatomical, and functional modifications that impact respiratory muscle strength. This thesis, comprising two articles as outcomes, aimed to. 1) Evaluate the influence of sitting, supine with the head elevated at 45°, and supine body positions and the electrical activity of respiratory muscles during measurements of Maximal Inspiratory Pressure (MIP), Maximal Expiratory Pressure (MEP), Nasal Inspiratory Pressure (SNIP), and Nasal Expiratory Pressure (SNEP) in self-declared healthy subjects. 2) Assess the influence of sitting and supine with the head elevated at 45° positions and the electrical activity of respiratory muscles during SNIP and SNEP measurements in subjects with DMD compared to matched healthy individuals. Methods: 1) In the sitting, 45° supine, and supine positions, the activation of the respiratory muscles sternocleidomastoid (SCM), scalene (SC), rectus abdominis (RA), and intercostals (IC) was evaluated using surface electromyography (sEMG) during the MIP, MEP, SNIP, and SNEP maneuvers in self-declared healthy individuals. 2) In the sitting and 45° supine positions, the activation of the respiratory muscles sternocleidomastoid (SCM), scalene (SC), rectus abdominis (RA), and external oblique (EO) was evaluated using surface electromyography (sEMG) during the SNIP and SNEP maneuvers in individuals with DMD (Duchenne group, DG), paired with healthy subjects (control group, CG). Results: 1) Ten healthy individuals were evaluated, equally divided between five men and five women. In this group, SNIP and SNEP values were significantly higher in the sitting position compared to the supine position (P < 0.05). Intercostal (IC) muscle activity was greater during the MIP, MEP, and SNEP maneuvers in the sitting position (P < 0.05). Additionally, rectus abdominis (RA) activity was higher in this position during the MIP and SNEP maneuvers (P < 0.05). 2) Fifteen individuals with Duchenne muscular dystrophy (DMD) were initially included (four excluded), resulting in 11 subjects forming the Duchenne group (DG), paired with 11 healthy subjects (control group, CG). DG subjects showed lower SNIP and SNEP values compared to CG (P < 0.05). Electromyographic activity of the sternocleidomastoid (SCM), scalene (SC), and rectus abdominis (RA) muscles during maneuvers was lower in DG versus CG in the sitting position and lower in RA in the 45° supine position when comparing the same groups (P < 0.05). In intragroup analyses, SCM, SC, and RA electromyographic activity was higher in the sitting position than in the 45° supine position in DG (P < 0.05). In CG, SCM electromyographic activity was higher in the sitting position than in the 45° supine position (P < 0.05). Conclusion: Our results demonstrate that, in both individuals with DMD and healthy subjects, the pressures generated during SNIP and SNEP maneuvers, as well as sEMG activity in all maneuvers, are optimized when the trunk is in a more upright position.