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Emmanuel Futier, MD; Samir Jaber, MD, PhD; Jean-Michel Constantin, MD, PhD
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From the Department of Anesthesiology and Critical Care Medicine (Drs Futier and Constantin), Estaing Hospital, University Hospital of Clermont-Ferrand; and Department of Anesthesiology and Critical Care Medicine B (Dr Jaber), Saint Eloi Hospital, University Hospital of Montpellier.

Correspondence to: Emmanuel Futier, MD, Département d’Anesthésie et Réanimation (DAR), Hôpital Estaing, Centre Hospitalier Universitaire de Clermont-Ferrand, 1 Place Lucie Aubrac, 63000 Clermont-Ferrand CEDEX 1, France; e-mail: efutier@chu-clermontferrand.fr


Financial/nonfinancial disclosures: The authors have 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):1181-1182. doi:10.1378/chest.12-2497
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To the Editor:

We thank Dr Esquinas for his comments on and interest in our study.1 We agree that a physiologic evaluation cannot resolve all uncertainties and that further studies are mandatory to define the scope of the neurally adjusted ventilator assist (NAVA) mode. That being said, we would like to address his comments.

First, we are doubtful about the proposed contribution of diaphragmatic activity in the recruitment of poorly (or not) aerated lung areas, which refers to a dynamic process of reopening collapsed lung units through a transient increase in transpulmonary pressure.2 The same applies for the possible correlation between an improved patient-ventilator interaction with the NAVA mode and an increase in the oxygenation index, which is a complex parameter that depends on multiple factors, such as flow and cardiac index. Although no difference in oxygenation was evident between the two study groups, each of the two modes (pressure support ventilation and NAVA) significantly improved oxygenation during noninvasive ventilation (NIV) compared with baseline. This is, to some extent, good news in that NAVA can be reliably and safely delivered to patients receiving NIV.

Second, although we agree that some of the patients could have benefited from higher positive end-expiratory pressure levels, both positive end-expiratory pressure (between 5 and 10 cm H2O) and tidal volume setting (to achieve a tidal volume of 6-8 mL/kg of ideal body weight) were (1) standardized to reflect common clinical practice during NIV for acute respiratory failure3,4 and (2) close to that used by Terzi and colleagues5 in the physiologic evaluation of patients with ARDS. Third, we agree that excessive levels of assistance could affect the asynchrony index during NIV. Nevertheless, the difference in tidal volumes was not significant (pressure support ventilation group, 8 mL/kg [range, 6-8 mL/kg]; NAVA group, 8 mL/kg [7-8 mL/kg]; P = .08) and, in any event, was not clinically relevant. Finally, we are convinced that physiologic assessment is an indispensable prerequisite of clinical application and an adds to our knowledge.

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]
 
Constantin JM, Cayot-Constantin S, Roszyk L, et al. Response to recruitment maneuver influences net alveolar fluid clearance in acute respiratory distress syndrome. Anesthesiology. 2007;106(5):944-951. [CrossRef] [PubMed]
 
Ferrer M, Esquinas A, Leon M, Gonzalez G, Alarcon A, Torres A. Noninvasive ventilation in severe hypoxemic respiratory failure: a randomized clinical trial. Am J Respir Crit Care Med. 2003;168(12):1438-1444. [CrossRef] [PubMed]
 
Carrillo A, Gonzalez-Diaz G, Ferrer M, et al. Non-invasive ventilation in community-acquired pneumonia and severe acute respiratory failure. Intensive Care Med. 2012;38(3):458-466. [CrossRef] [PubMed]
 
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]
 

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References

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]
 
Constantin JM, Cayot-Constantin S, Roszyk L, et al. Response to recruitment maneuver influences net alveolar fluid clearance in acute respiratory distress syndrome. Anesthesiology. 2007;106(5):944-951. [CrossRef] [PubMed]
 
Ferrer M, Esquinas A, Leon M, Gonzalez G, Alarcon A, Torres A. Noninvasive ventilation in severe hypoxemic respiratory failure: a randomized clinical trial. Am J Respir Crit Care Med. 2003;168(12):1438-1444. [CrossRef] [PubMed]
 
Carrillo A, Gonzalez-Diaz G, Ferrer M, et al. Non-invasive ventilation in community-acquired pneumonia and severe acute respiratory failure. Intensive Care Med. 2012;38(3):458-466. [CrossRef] [PubMed]
 
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]
 
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