The purpose of section 3 is to outline the process by which the parameters for NIV-NAVA are set. In contrast to conventional ventilator which use either flow or pressure as trigger, NAVA ventilation uses neural trigger (diaphragmatic EMG) to deliver mechanical breaths that are synchronised to initiation, size and termination with each patient’s breath. The flow chart below explains the principle behind NAVA.
The electrical activity of the diaphragm is detected by electrodes embedded in a special nasogastric tube positioned in the lower oesophagus at the level of crural diaphragm and transmitted via wires in the NGtube to the ventilator. The peak inspiratory pressure delivered is based on the amount of electric activity generated by the diaphragm. Inspiration (pressure delivery) is maintained until the electrical activity decreases by 30% of the peak pressure generated and the breath is then terminated. The terminologies used in NAVA and their significance are: