This manuscript describes the motivation for developing neurally adjusted ventilatory assist (NAVA) and its subsequent use with a non-invasive interface. The challenges with conventional, pneumatically controlled non-invasive modes are briefly described, followed by a mini-review on the upper airways and the diaphragm electrical activity (EAdi) signal. The bulk of the review focuses on the importance and use of monitoring the EAdi during non-invasive ventilation, and a report of the recent experimental and clinical findings with NAVA during non-invasive ventilation. In summary, non-invasive NAVA provides a truly synchronized mode of non-invasive ventilation, both in time and in level of assist. Along with EAdi monitoring, NAVA can increase the confidence to treat respiratory failure non-invasively.