Efeitos agudos das cargas inspiratórias nos volumes da parede torácica e atividade elétrica dos músculos respiratórios em adultos saudáveis e crianças respiradores orais

Abstract

Introduction: Mouth breathing (MB) most commonly found in children is a respiratory disorder in which the subject adopts an oral mode to supplement or totally replace the normal nasal breathing. This disorder results in an imbalance of the stomatognathic system, which leads to structural changes in the jaws and changes in posture, speech, swallowing, sleep and breathing. Nasal breathing is the physiologic pattern and has advantages when compared to oral breathing. However, the respiratory resistance devices available in the market use mouthpieces (oral airway). The use of inspiratory overloads aims to improve endurance and muscle strength to improve lung function, for this, different modalities of respiratory muscle training have been reported in the literature. Based on what has been described this thesis presents two studies resulting from its research line: 1) a study of the use of inspiratory overloads with different interfaces in healthy adult subjects and 2) a second study of the use of inspiratory overloads via nasal airway with different inspiratory resistance devices in mouth breathing children. Aims: The aim of this thesis was to evaluate the acute effects of different inspiratory overloads intensities, different interfaces and different inspiratory resistance devices on the breathing pattern and respiratory muscle activity of healthy adult subjects and mouth breathing children. Methods: 1) Twenty healthy adults were recruited and assigned to two groups based on inspiratory load intensity (20 and 40% of the Maximal Inspiratory Pressure) by way of randomized crossover allocation. Subjects were evaluated during quiet breathing, breathing against inspiratory load, and recovery. The measurements were repeated using two different interfaces (nasal and oral). 2) Thirty-nine children with mouth breathing syndrome (MBS) were randomized into two groups based on inspiratory load intensity (20% and 40% of the Maximal Inspiratory Pressure). These children were assessed during quiet breathing, breathing against inspiratory load via nasal airway and recovery. The measurements were repeated using two different devices (pressure threshold and flow resistance). In both studies during the intervention protocol, chest wall volumes and respiratory muscles activity were evaluated by optoelectronic plethysmography and surface electromyography, respectively. Results: 1) During the application of inspiratory load, significant changes were observed in the respiratory rate (p < 0.04), inspiratory time (p < 0.02), minute ventilation (p < 0.04), tidal volume (p < 0.01), end-inspiratory volume (p < 0.04), end-expiratory volume (p < 0.03), and in the activity of the scalene, sternocleiomastoid, and parasternal portion of the intercostal muscles (RMS values, p < 0.01) when compared to quiet breathing, regardless of the load level or the interface applied. Inspiratory load application generated an increase in the tidal volume (p < 0.01), end-inspiratory volume (p < 0.01), and electrical activity of the scalene and sternocleiomastoid muscles (p < 0.01) with the use of nasal interface when compared to oral. 2) During the application of inspiratory load, significant changes occurred in respiratory rate (p<0.04), inspiratory time (p<0.02), total time of respiratory cycle (p<0.02), minute volume (p<0.03), tidal volume (p<0.01) and scalene and sternocleidomastoid muscles activity (RMS values, p<0.01) when compared to quiet spontaneous breathing and recovery, regardless of load level or device applied. The application of inspiratory load using the flow resistance device showed an more increase in the tidal volume (p<0.02) and end-inspiratory volume (p<0.02) when compared to pressure threshold. Conclusion: Both studies open new physiological and therapeutic perspectives. These are precursor studies regarding the assessment of chest wall volumes and compartments, as well as the analysis of the electrical activity of respiratory muscles. Study 1 shows that the addition of inspiratory loading has a significant effect on the breathing pattern and electrical activity of respiratory muscles, and these effects are greater when the nasal interface is applied. Study 2 shows that the addition of inspiratory loading using a nasal interface has a positive effect on the breathing pattern and electrical activity of inspiratory muscles, and the FR device was more effective for lung volume generation.