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.
    Full-text · Article · Feb 2014 · BMC Pulmonary Medicine
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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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    ABSTRACT: Neurally adjusted ventilatory assist (NAVA) delivers pressure in proportion to diaphragm electrical activity (Eadi). However, each patient responds differently to NAVA levels. This study aims to examine the matching between tidal volume (Vt) and patients' inspiratory demand (Eadi), and to investigate patient-specific response to various NAVA levels in non-invasively ventilated patients. 12 patients were ventilated non-invasively with NAVA using three different NAVA levels. NAVA100 was set according to the manufacturer's recommendation to have similar peak airway pressure as during pressure support. NAVA level was then adjusted +/-50% (NAVA50, NAVA150). Airway pressure, flow and Eadi were recorded for 15 minutes at each NAVA level. The matching of Vt and integral of Eadi ([latin small letter esh]Eadi) were assessed at the different NAVA levels. A metric, Range90, was defined as the 5-95% range of Vt/[latin small letter esh]Eadi ratio to assess matching for each NAVA level. Smaller Range90 values indicated better matching of supply to demand. Patients ventilated at NAVA50 had the lowest Range90 with median 25.6 uVs/ml [Interquartile range (IQR): 15.4-70.4], suggesting that, globally, NAVA50 provided better matching between [latin small letter esh]Eadi and Vt than NAVA100 and NAVA150. However, on a per-patient basis, 4 patients had the lowest Range90 values in NAVA100, 1 patient at NAVA150 and 7 patients at NAVA50. Robust coefficient of variation for [latin small letter esh]Eadi and Vt were not different between NAVA levels. The patient-specific matching between [latin small letter esh]Eadi and Vt was variable, indicating that to obtain the best possible matching, NAVA level setting should be patient specific. The Range90 concept presented to evaluate Vt/[latin small letter esh]Eadi is a physiologic metric that could help in individual titration of NAVA level.
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    No preview · Article · Jan 2012 · Medicina Intensiva
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