• Y Somers, W Verbrugghe, and P G Jorens.
• Department of Critical Care Medicine, Antwerp University Hospital, University of Antwerp, Antwerp, Belgium - Philippe.Jorens@uza.be.
• Minerva Anestesiol. 2013 Dec 1;79(12):1436-42.

BackgroundNeurally Adjusted Ventilatory Assist (NAVA) offers synchronized proportional pressure in accordance with the electrical activity of the diaphragm (EAdi). NAVA relies on the EAdi to trigger the respiratory cycle and then adjusts the ventilatory assist to the neural drive. The technique necessitates a catheter with bipolar microelectrodes positioned near the crural diaphragm where this signal can be captured. Capturing a reliable EAdi signal is a condition sine qua non for using NAVA as a mode of ventilation. The displayed signal represents the sum of the electrical activity of the muscle action potential of the diaphragm and is expressed in microvolts.MethodsA technical note illustrated by a case series in the intensive care unit (ICU) of a tertiary referral hospital with experience using NAVA.ResultsHere, we report on three separate cases in which the use of an intra-aortic balloon catheter, a pacemaker and a heating device all resulted in a distortion of the EAdi signal, despite good positioning of the catheter. In a fourth case, we observed internal interference from leaking cardiac electrical activity due to the malpositioning of the EAdi catheter in a patient with atrial fibrillation.ConclusionWe illustrate that the detection and therefore interpretation of the EAdi signal during NAVA can be influenced by mechanical and electrical interference by other equipment used in the ICU or from endogenous leaking cardiac activity.

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