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: 7.48). 05/2012; 143(1). DOI: 10.1378/chest.12-0424
Source: PubMed


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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Available from: Pierre-Marie Bertrand, Jul 24, 2015
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    • "A number of strategies can be implemented to avoid “gross asynchronies,” such as optimization of ventilator settings using the screen ventilator waveforms, adjusting trigger sensitivity, increasing positive end-expiratory pressure, minimizing leaks, using different modes or more sophisticated ventilators [33]. New modes of ventilation, such as neutrally adjusted ventilator assist, have been documented to reduce asynchrony [34]. "
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    ABSTRACT: Identifying the predictors of noninvasive ventilation (NIV) failure has attracted significant interest because of the strong link between failure and poor outcomes. However, very little attention has been paid to the timing of the failure. This narrative review focuses on the causes of NIV failure and risk factors and potential remedies for NIV failure, based on the timing factor. The possible causes of immediate failure (within minutes to <1 h) are a weak cough reflex, excessive secretions, hypercapnic encephalopathy, intolerance, agitation, and patient-ventilator asynchrony. The major potential interventions include chest physiotherapeutic techniques, early fiberoptic bronchoscopy, changing ventilator settings, and judicious sedation. The risk factors for early failure (within 1 to 48 h) may differ for hypercapnic and hypoxemic respiratory failure. However, most cases of early failure are due to poor arterial blood gas (ABGs) and an inability to promptly correct them, increased severity of illness, and the persistence of a high respiratory rate. Despite a satisfactory initial response, late failure (48 h after NIV) can occur and may be related to sleep disturbance. Every clinician dealing with NIV should be aware of these risk factors and the predicted parameters of NIV failure that may change during the application of NIV. Close monitoring is required to detect early and late signs of deterioration, thereby preventing unavoidable delays in intubation.
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    • "No significant intra-patient difference between NAVA levels was found in the variability of ʃEadi, Pin, Vt, and Ti. This result indicates that ventilation at different NAVA levels results in similar variability [7,11,13,17-19]. Thus, selecting an optimal NAVA level for a patient based on variability analysis is not suitable. "
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