Neurally Adjusted Ventilatory Assist (NAVA): An Update and Summary of Experiences

Neurally adjusted ventilatory assist (NAVA) is a mode of mechanical ventilation delivering pressure in response to the patient's respiratory drive (measured by the electrical activity of the diaphragm, EAdi). Hence, NAVA acts as an external "respiratory muscle pump" controlled by the patient's EAdi, which in turn is influenced by res- piratory feedback mechanisms. This review describes the "fundamentals" of NAVA and reports results from physi- ological studies on NAVA in animals and humans. The results demonstrate that NAVA maintains subject-ventilator synchrony, adapts to altered respiratory demand, and delivers tidal volumes and mean airway pressures that can be considered protective. Moreover, there is evidence suggesting that NAVA maintains synchrony even in the pres- ence of leaks, one of the current major limitations of non-invasive positive pressure ventilation. Besides the use of the EAdi to control the respirator, monitoring the EAdi provides information about the neural respiratory drive and breathing pattern and the response of these parameters to various treatments and interventions. In summary, NAVA improves monitoring of respiratory drive, and delivers synchronized assist in relation to patient effort, and the con- trol of assist is not affected by leaks.