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Correspondence |

Neurally Adjusted Ventilatory Assist vs Pressure Support Ventilation During Noninvasive Mechanical VentilationNoninvasive Mechanical Ventilation: Another Physiologic Evaluation to Consider? FREE TO VIEW

Antonio M. Esquinas, MD, PhD, FCCP
Author and Funding Information

From the Intensive Care Unit, Hospital Morales Meseguer.

Correspondence to: Antonio M. Esquinas, MD, PhD, FCCP, Intensive Care Unit, Hospital Morales Meseguer, Avenida Marques de Los Velez, s/n, Murcia, 3088-Spain; e-mail: antmesquinas@gmail.com


Financial/nonfinancial disclosures: The author has reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2013;143(4):1181. doi:10.1378/chest.12-2412
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Published online
To the Editor:

Neurally adjusted ventilatory assist (NAVA) is an original approach to noninvasive ventilation that can improve patient-ventilator interaction and may influence physiologic outcomes1-3 because the electrical activity of the diaphragm, a pneumatically independent signal, is used to control the timing and level of assist provided, regardless of the interface used. In a recent issue of CHEST (January 2013), Bertrand et al4 compared patient-ventilator interaction during pressure support ventilation (PSV) and NAVA applied noninvasively and showed reductions in all of the following with NAVA: ineffective efforts, trigger and cycling-off delays, and inspiratory times. This, thus, demonstrated a lower “severe asynchrony” (“severe” defined by an asynchrony index >10%), but despite these positive findings in patient-ventilator interaction, the clinical impact was not so clear and deserves comment.

First, there were no significant changes in the oxygenation index when patient-ventilator synchrony improved with NAVA. This finding is relevant because it is not in accordance with the findings of previous studies.1,3 It could be hypothesized that the restoration of diaphragmatic activity contributes to a recruitment of poorly ventilated areas. In this study, were the selected positive end-expiratory pressures too low and were the observation periods too short? Furthermore, in terms of practical implications, is the expected oxygenation improvement correlated to a reduced patient-ventilator asynchrony index or to independent factors?4,5

Second, the ventilatory parameters selected (PSV and positive end-expiratory pressure) were restricted and were applied for short observation times, which may have limited the extension of the results outside this protocol. Third, the tidal volume during PSV was significantly higher than during NAVA (Table 3,4 tidal volume 515 mL [410-593] in the PSV group, 498 mL [421-663] in the NAVA group). Does this finding affect the PSV-increased asynchrony index in this group? Moreover, were the selection parameters of PSV high or did they not require pressure support but simply continuous positive airway pressure? We can hypothesize that the high level of tidal volume was responsible for the asynchrony.2 Furthermore, we may ask what are the criteria for tidal volume selection and its relationship with the uncomfortable respiratory pattern of the PSV trial?

One final interesting question is, how do physiologic studies influence the discomfort during PSV and NAVA and what is the degree of correlation? No information regarding the involvement of the respiratory center and the subsequent discomfort is reported. Does one need to know how the brain operates to understand the lungs? Or is this another physiologic evaluation to consider? This is an open question that may influence results and interpretation.

References

Terzi N, Pelieu I, Guittet L, et al. Neurally adjusted ventilatory assist in patients recovering spontaneous breathing after acute respiratory distress syndrome: physiological evaluation. Crit Care Med. 2010;38(9):1830-1837. [CrossRef] [PubMed]
 
Piquilloud L, Tassaux D, Bialais E, et al. Neurally adjusted ventilatory assist (NAVA) improves patient-ventilator interaction during non-invasive ventilation delivered by face mask. Intensive Care Med. 2012;38(10):1624-1631. [CrossRef] [PubMed]
 
Thille AW, Rodriguez P, Cabello B, Lellouche F, Brochard L. Patient-ventilator asynchrony during assisted mechanical ventilation. Intensive Care Med. 2006;32(10):1515-1522. [CrossRef] [PubMed]
 
Bertrand P-M, Futier E, Coisel Y, Matecki S, Jaber S, Constantin J-M. Neurally adjusted ventilator assist vs pressure support ventilation for noninvasive ventilation during acute respiratory failure: a crossover physiologic study. Chest. 2013;143(1):30-36. [PubMed]
 
Allo JC, Beck JC, Brander L, Brunet F, Slutsky AS, Sinderby CA. Influence of neurally adjusted ventilatory assist and positive end-expiratory pressure on breathing pattern in rabbits with acute lung injury. Crit Care Med. 2006;34(12):2997-3004. [PubMed]
 

Figures

Tables

References

Terzi N, Pelieu I, Guittet L, et al. Neurally adjusted ventilatory assist in patients recovering spontaneous breathing after acute respiratory distress syndrome: physiological evaluation. Crit Care Med. 2010;38(9):1830-1837. [CrossRef] [PubMed]
 
Piquilloud L, Tassaux D, Bialais E, et al. Neurally adjusted ventilatory assist (NAVA) improves patient-ventilator interaction during non-invasive ventilation delivered by face mask. Intensive Care Med. 2012;38(10):1624-1631. [CrossRef] [PubMed]
 
Thille AW, Rodriguez P, Cabello B, Lellouche F, Brochard L. Patient-ventilator asynchrony during assisted mechanical ventilation. Intensive Care Med. 2006;32(10):1515-1522. [CrossRef] [PubMed]
 
Bertrand P-M, Futier E, Coisel Y, Matecki S, Jaber S, Constantin J-M. Neurally adjusted ventilator assist vs pressure support ventilation for noninvasive ventilation during acute respiratory failure: a crossover physiologic study. Chest. 2013;143(1):30-36. [PubMed]
 
Allo JC, Beck JC, Brander L, Brunet F, Slutsky AS, Sinderby CA. Influence of neurally adjusted ventilatory assist and positive end-expiratory pressure on breathing pattern in rabbits with acute lung injury. Crit Care Med. 2006;34(12):2997-3004. [PubMed]
 
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