Nicolo ` Patroniti Giacomo Bellani Erica Saccavino Alberto Zanella Giacomo Grasselli Stefano Isgro ` Manuela Milan Giuseppe Foti Antonio Pesenti Respiratory pattern during neurally adjusted ventilatory assist in acute respiratory failure patients Received: 9 March 2011 Accepted: 7 November 2011 Published online: 30 November 2011 Ó Copyright jointly held by Springer and ESICM 2011 Electronic supplementary material The online version of this article (doi:10.1007/s00134-011-2433-8) contains supplementary material, which is available to authorized users. N. Patroniti ( ) ) Á G. Bellani Á A. Zanella Á S. Isgro ` Á M. Milan Á A. Pesenti Department of Experimental Medicine, University of Milan-Bicocca, via Cadore 48, 20048 Monza, Milan, Italy e-mail: nicolo.patroniti@unimib.it Tel.: ?39-039-2339273 Fax: ?39-039-2332297 N. Patroniti Á G. Bellani Á E. Saccavino Á G. Grasselli Á G. Foti Á A. Pesenti Department of Emergency Medicine and Intensive Care, San Gerardo Hospital, via Pergolesi 33, 20052 Monza, Milan, Italy Abstract Purpose: To investigate the effect of a wide range of assis- tance levels during neurally adjusted ventilatory assist (NAVA) and pres- sure support ventilation (PSV) on respiratory pattern, breathing vari- ability, and incidence of tidal volumes (V T ) above 8 and 10 ml/kg in acute respiratory failure patients. Methods: Eight increasing NAVA levels (0.5, 1, 1.5, 2, 2.5, 3, 4, and 5 cmH 2 O/lV) and four increasing pressure support (PSV) levels (4, 8, 12, and 16 cmH 2 O) were applied to obtain 10 min of stable recordings in 15 patients. Results: One out of 15 patients did not sustain the NAVA levels of 3, 4, and 5 cmH 2 O/lV and was excluded. The 5 cmH 2 O/lV NAVA level was not tolerated by three patients and it was excluded. Increasing NAVA levels were asso- ciated with decreased diaphragm electrical activity (EAdi), and, at variance with PSV, with small changes in V T , no changes in respi- ratory rate (RR), and increases in V T and EAdi variability. At high NAVA levels, an increase in V T variability was associated with increased inci- dence of V T above 8 and 10 ml/kg and an uncomfortable respiratory pattern in some patients. Conclu- sions: Increasing NAVA levels were associated with no effect on RR, small increase in V T , and increase in V T and EAdi variability. Effective decrease in EAdi occurred at NAVA levels below 2–2.5 cmH 2 O/lV, while preserving respiratory variability and low risks of V T above 8 or 10 ml/kg. Keywords Pressure support ventilation Á Acute respiratory failure Á Neurally adjusted ventilatory assist Á Respiratory pattern Introduction Neurally adjusted ventilatory assist (NAVA) is a novel mode of mechanical ventilation during which the pressure applied by the ventilator to the airways during inspiration is proportional to the diaphragm electrical activity (EAdi) according to a multiplicative factor called ‘‘NAVA level’’ [1]. Studies on healthy volunteers [2], acute respiratory failure (ARF) patients [3–7], newborns [8, 9], and animal models [10–13] have shown that NAVA can efficiently unload the respiratory muscles. Clinical studies on NAVA suggest that there is a different physiologic response in respiratory pattern to changing levels of assistance than that commonly observed during pressure support venti- lation (PSV) [3–8, 14]. However, most of the available data come from studies where either each NAVA level was applied for only 3 min [5] or only a narrow range of NAVA levels was applied [3, 4]. Moreover, some potentially relevant aspects of NAVA have not been investigated in the clinical setting. First, given the strict interdependency between EAdi and ventilatory output variables, during NAVA the effects Intensive Care Med (2012) 38:230–239 DOI 10.1007/s00134-011-2433-8 ORIGINAL