Métodos de normalização e análise da atividade elétrica dos músculos respiratórios em indivíduos com esclerose lateral amiotrófica e sujeitos saudáveis

Abstract

Introduction: Surface electromyography (sEMG) is one of the methods used to assess the electrical activity of muscles, whether at rest, during functional activity or during exercise. sEMG can be used to assess skeletal and respiratory muscles in individuals in various health and disease states, allowing comparisons between different days, individuals and specific tasks. Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterised by generalised muscle weakness. One of the leading causes of death in these people is respiratory muscle weakness, which leads to respiratory failure. sEMG is becoming an important tool for monitoring respiratory muscles in people with ALS, allowing an understanding of muscle recruitment patterns and potential dysfunction in these subjects. The electromyographic signal can be influenced by intrinsic and extrinsic factors. It is therefore important to explore methods to minimise the interference of these factors to ensure that the results are as accurate as possible. One approach to this is normalisation. However, there is still no consensus in the literature on the best way to normalise the electromyographic signal. This thesis is divided into two chapters and presents the results of the research in two scientific articles. The aims of this work were: Aim of Article 1: To compare different methods of normalising the sEMG signal of the respiratory muscles in individuals with ALS and healthy subjects; Aim of Article 2: To analyse the electrical activity and the contraction and relaxation variables of the sternocleidomastoid and scalene muscles during the sniff nasal inspiratory pressure (SNIP) manoeuvre in individuals with ALS and healthy subjects using surface electromyography. Methodology: This is a cross-sectional study, approved by the University Ethics Committee under protocol number 3.127.064, involving 67 participants, 50 from the healthy group and 17 from the ALS group. The electrical activity of the sternocleidomastoid (SCM), scalene (SCA), diaphragm (DIA), parasternal (PS), external intercostal (EI), external oblique (EO) and rectus abdominis (RA) muscles was analysed during the following manoeuvres maximal inspiratory pressure (MIP), nasal inspiratory pressure (SNIP), maximal expiratory pressure (MEP) and maximal voluntary isometric contraction of the SCM and SCA (MVICSCM/SCA) and RA (MVICRA). Comparisons of sEMG were made taking into account the division of manoeuvres and muscles into inspiratory and expiratory categories. In addition, electrical activity of the SCM and SCA muscles during the SNIP manoeuvre was analysed along with contraction time (CT), relaxation time (RT), total time (TT) and pressure-time ratio variables based on sEMG data from 24 subjects (12 ALS group and 12 healthy subjects). Results: In the healthy group, inspiratory and expiratory muscles showed greater electrical activity during the MVICSCM/SCA and MVICRA manoeuvres, respectively (p<0.05). In the ALS group, this activity was higher only during the SNIP manoeuvre compared to MIP for inspiratory muscles, whereas for expiratory muscles it was higher during MVICRA compared to MEP (p<0.05). During the SNIP manoeuvre, a difference in electrical activity (RMS) of the SCM and SCA muscles was observed between groups, with healthy subjects showing higher RMS values (p<0.05). In addition, subjects with ALS had a longer CT, shorter RT and reduced pressure-time ratio in the SCM muscle. Conclusion: The normalisation method based on MVIC was the one in which the respiratory muscles showed the highest electrical activity, both for the set of manoeuvres considered as inspiratory and expiratory in healthy subjects. In people with ALS, the SNIP manoeuvre appears to be the most appropriate for normalising the inspiratory muscles, while MVIC is more appropriate for the expiratory muscles. It was also observed that in individuals with ALS there was an increase in CT and a decrease in RT of the SCM muscle, suggesting that sEMG evaluation of this muscle may be useful in monitoring disease progression.