Neurally adjusted ventilatory assist

Neurally adjusted ventilatory assist (NAVA) is a form of ventilator support in which the electrical activity of the diaphragm (EAdi) drives the ventilator. The signal, obtained from the crural portion of the diaphragm via a nasogastric or orogastric feeding tube, is transformed into a waveform that is utilised to regulate the inspiratory assistance. The ventilator applies pressure to the airway throughout inspiration in proportion to EAdi, which is multiplied by an adjustable gain constant (NAVA level). With NAVA, both the timing and the magnitude of ventilator delivered assistance are controlled by the EAdi. In contrast with the conventional pneumatically-driven modes, NAVA has been shown to improve patient- ventilator interaction and yield a remarkable reduction in any asynchronies. Furthermore, with NAVA the patient retains control of her/his breathing pattern, which is more variable in nature; this variability might determine improved oxygenation in patients with acute lung-volume reduction. Because tidal volume is not remarkably increased when augmenting the NAVA level, this novel mode has the potential to maintain protective ventilation in spontaneously breathing patients.