Acute effects of inspiratory loads on chest wall volumes and electrical activity of respiratory muscles in healthy adults and mouth breathing children
Keywords: Electromyography; Plethysmography. Respiratory Function Tests; Healthy subjects; Respiratory muscles; Mouth breathing; Children.
ABSTRACT
Aims: 1) The aim of this study was to evaluate the acute effects of different inspiratory loads and different interfaces on the breathing pattern and activity of the respiratory muscles. 2) The aim of this study was to evaluate the acute effects of different inspiratory resistance devices and intensity of loads via nasal airway on the breathing pattern and activity of the respiratory muscles in children with mouth breathing syndrome. Methods: 1) Twenty healthy adults were recruited and assigned to two groups (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). Chest wall volumes and respiratory muscle activity were assessed with optoelectronic plethysmography and surface electromyography, respectively. 2) 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 (PT) and flow resistance (FR)). 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 yielded significant differences between using nasal and oral interfaces with 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) seen with using the nasal interface. 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 FR device showed an more increase in the tidal volume (p<0.02) and end-inspiratory volume (p<0.02) when compared to PT. Conclusion: 1) The addition of an inspiratory load has a significant effect on the breathing pattern and respiratory muscle electrical activity, and the effects are greater when the nasal interface is applied. 2) The addition of inspiratory loads using a nasal interface has a positive effect on the breathing pattern and electrical activity of the inspiratory muscles, and the FR device is more effective for lung volume generation.