Non-invasive mechanical ventilation is useful in order to delay or avoid endotracheal intubation. Continuous positive airway pressure (CPAP) is helpful for patients with decreased lung compliance, airways obstruction due to vocal cord paralysis or tracheobronchomalacia, presence of auto-PEEP (positive end-expiratory pressure) and as a weaning method. Non-invasive intermittent positive pressure ventilation (IPPV) is not very different from conventional mechanical ventilation except for the absence of an endotracheal tube. It is specially useful in patients with neuromuscular diseases or central hypoventilation. It has been also helpful for patients with decrease of lung compliance or COPD and as a weaning procedure. It may be applied with or without PEEP and by means of a bi-level IPPV system. All of these methods require cooperative patients and by means of a bi-level IPPV system. All of these methods require cooperative patients and they do not allow an adequate management of increased respiratory secretions. Non-invasive mechanical ventilation has the advantages of not showing complications associated to endotraqueal intubation and may be performed by means of less expensive equipment.