Neurally Adjusted Ventilatory Assist vs Pressure Support Ventilation for Noninvasive Ventilation During Acute Respiratory Failure A Crossover Physiologic Study

1Department of Anesthesiology and Critical Care, Estaing Hospital, University Hospital of Clermont-Ferrand, Clermont-Ferrand, France. Email: .
Chest (Impact Factor: 7.13). 05/2012; 143(1). DOI: 10.1378/chest.12-0424
Source: PubMed

ABSTRACT ABSTRACT BACKGROUND:Patient-ventilator asynchrony is common during noninvasive ventilation (NIV) with pressure support ventilation (PSV). We examined the effect of neurally adjusted ventilator assist (NAVA) delivered through a facemask on synchronization in patients with acute respiratory failure (ARF). METHODS:This was a prospective physiological crossover study of 13 patients with ARF (median PaO(2)/FiO(2) 196 [IQR: 142-225]) given two 30-min trials of NIV with PSV and NAVA in random order. Diaphragm electrical activity (EAdi), neural inspiratory time (Tin), trigger delay, asynchrony index (AI), arterial blood gases (ABGs), and patient discomfort were recorded. RESULTS:There were significantly fewer asynchrony events during NAVA than PSV (10 [IQR: 5-14] events vs. 17 [IQR: 8-24] events, p = 0.017) and the occurrence of severe asynchrony (AI > 10%) was also less under NAVA (p = 0.027). Ineffective efforts and delayed cycling were significantly less with NAVA (p < 0.05 for both). NAVA was also associated with reduced trigger delay (0 [IQR: 0-30] ms vs. 90 [IQR: 30-130] ms, p < 0.001) and inspiratory time in excess (10 [IQR: 0-28] ms vs. 125 [IQR: 20-312] ms, p < 0.001), but Tin was similar under PSV and NAVA. EAdi max was higher during NAVA than PSV (p = 0.017). There were no significant differences in ABGs and patient discomfort under PSV and NAVA. CONCLUSION:In view of specific experimental conditions, our comparison of PSV and NAVA indicated that NAVA significantly reduced severe patient-ventilator asynchrony and resulted in similar improvements in gas exchange during NIV for ARF.Trial registry: No. NCT01426178.

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    ABSTRACT: Patient-ventilator interaction represents an important clinical challenge during non-invasive ventilation (NIV). Doorduin and colleagues' study shows that non-invasive neurally adjusted ventilatory assist (NAVA) improves patient-ventilator interaction compared with pressure support ventilation in patients with chronic obstructive pulmonary disease. There is no doubt nowadays that NAVA is the most effective mode of improving the synchrony between patient and machine, but the key question for the clinicians is whether or not this will make a difference to the patient's outcome. The results of the study still do not clarify this issue because of the very low clinically important dyssynchrony, like wasted efforts, in the population studied. Air leaks play an important role in determining patient-ventilator interaction and therefore NIV success or failure. Apart from the use of a dedicated NIV ventilator or specific modes of ventilation like NAVA, the clinicians should be aware that the choice of interface, the humidification system and the appropriate sedation are key factors in improving patient-ventilator synchrony.
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