Neurally adjusted ventilatory assist (NAVA) is a relatively new mode of partial ventilatory support, allowing the triggering and driving of the ventilatory support to be proportional to the electrical activity of the diaphragm (EAdi). Small clinical studies have suggested that NAVA can be beneficial, particularly by reducing patient-ventilator asynchrony . This study by Demoule and colleagues  is the first sizeable RCT to compare NAVA with pressure support ventilation (PSV) in adults weaning from invasive mechanical ventilation after acute respiratory failure. Results from this study were first presented at the annual congress of ESICM in October, 2016.
118 patients from 11 French ICUs (mixture of medical, surgical, and mixed ICUs) who had received >24hours endotracheal mechanical ventilation were included. They were expected to require >48hours of further mechanical ventilation, and suitable for weaning from a controlled mode to a supported mode of ventilation (as defined by pre-specified criteria).
They were randomised to either NAVA or PSV, aiming for tidal volumes of 6-8ml/kg of ideal body weight, and screened daily to identify readiness for extubation. All causes of acute respiratory failure were included (including acute cardiogenic pulmonary oedema and acute-on-chronic respiratory failure).
Primary outcome: the probability of remaining in a partial ventilatory mode (i.e. NAVA or PSV) throughout the first 48hours after randomisation, without return to assist-control ventilation.
• NAVA did not increase the probability of remaining in a partial ventilatory mode compared to PSV [67.2 vs. 63.3% (P=0.66)].
• NAVA reduced patient-ventilator asynchrony [14.7 vs. 26.7% (P<0.001)].
• NAVA did not reduce the duration of mechanical ventilation or ICU mortality.
• Feasibility and safety of NAVA over several days was successfully demonstrated.
Whilst this trial is likely to be viewed as a ‘negative trial’, it does demonstrate the ability to safely deliver NAVA partial ventilatory support for a prolonged period, and confirms that NAVA reduces patient-ventilator asynchrony.
This study has several limitations. It included all patients with acute respiratory failure, and so may have reduced the signal of benefit for those with difficult or prolonged respiratory weaning (where NAVA might have most benefit). It also only included highly experienced centres, which may have reduced the asynchrony/adverse event rate in the PSV group. It is also worth noting that the physicians in the PSV group were not blinded to the EAdi data for their patients – this may have affected their choice of PSV settings.
Take home message
NAVA is safe and feasible for weaning patients from mechanical ventilation, reduces asynchrony, but shows no overall benefit over PSV in a broad cohort of ICU patients with acute respiratory failure.
Article review prepared by Ehsan Ahmadnia on behalf of the ESICM Journal Review Club.
1. Piquilloud L, Vignaux L, Bialais E, Roeseler J, Sottiaux T, Laterre PF, Jolliet P, Tassaux D (2010) Neurally adjusted ventilatory assist improves patient-ventilator interaction. Intensive Care Med 37:263–271
2. Demoule A, Clavel M, Rolland-Debord C, Perbet S, Terzi N, Kouatchet A, Wallet F, Roze H, Vargas F, Guerin C, Dellamonica J, Jaber S, Brochard L, Similowski T (2016) Neurally adjusted ventilatory assist as an alternative to pressure support ventilation in adults: a French multicentre randomised trial. Intensive Care Med 42:1723–1732