Respiratory muscle testing allows a quantitative assessment of inspiratory and expiratory muscles in children of any age with primary or secondary respiratory muscle impairment, in order to better understand the pathophysiology of respiratory impairment and guide therapeutic management. The use of an invasive technique (esogastric probe) makes it possible to specifically explore the diaphragm, the accessory inspiratory muscles and the expiratory muscles in order to detect dysfunction or paralysis of these muscles, and to estimate the work of breathing in order to better guide the respiratory management. The primary objective of the study is to evaluate the respiratory effort in children with primary or secondary impairment of the respiratory muscles during spontaneous breathing or during mechanical ventilation.