A synchronous interaction of the patient and the ventilator is essential for successful mechanical ventilation, especially during non-invasive ventilation. However, in conventional pressure support modes with pneumatic triggering, a patient ventilator asynchrony may occur. In the relatively new mode called Neurally Adjusted Ventilatory Assist (NAVA), the electrical activity of the diaphragm (EADi) is detected by an oesophageal catheter equipped with electrodes in order to trigger the pressure support. The inspiratory pressure is initiated theoretically without delay and in proportion to the EADi signal, creating variable breathing patterns. Furthermore, the EADi signal provides valuable information about the neuro-respiratory coupling and the integrity of the diaphragm. NAVA can be applied as either non-invasive or invasive ventilation for infant or adult patients with different causes of respiratory failure. Technical aspects, settings, indications and current evidence on NAVA are summarised in this chapter.