The hypothesis is that a mechanical insufflation-exsufflation (MI-E) is associated with a decrease in the number of intubations and more rapid clinical improvement in children and adults with neuromuscular disease who are admitted for an acute respiratory exacerbation.In this prospective, randomised, multicenter study, 55 patients will be treated with standard treatment and a MI-E, and 55 patients with standard treatment and standard respiratory physiotherapy. The primary objective is the reduction of the number of patients requiring invasive ventilatory support (endotracheal intubation or tracheotomy) in the group treated with MI-E (MI-E group). The main secondary objectives are a reduction in hospital stay and an improvement in clinical condition, dyspnea and respiratory muscle function.