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Original Research: CRITICAL CARE MEDICINE |

Titration and Implementation of Neurally Adjusted Ventilatory Assist in Critically Ill Patients

Lukas Brander, MD; Howard Leong-Poi, MD; Jennifer Beck, PhD; Fabrice Brunet, MD; Stuart J. Hutchison, MD; Arthur S. Slutsky, MD; Christer Sinderby, PhD
Author and Funding Information

*From the Department of Critical Care Medicine (Dr. Brander), University Hospital-Inselspital, Bern, Switzerland; St. Michael's Hospital, Interdepartmental Division of Critical Care Medicine (Drs. Brunet, Beck, Slutsky, and Sinderby), University of Toronto, Toronto, ON, Canada; and the Division of Cardiology (Drs. Leong-Poi and Hutchison), St. Michael's Hospital, Toronto, ON, Canada. Some of the results have been presented in abstract format at the annual meetings of the European Society of Intensive Care Medicine in Barcelona, Spain, September 24 to 27, 2006, and of the American Thoracic Society in San Francisco, CA, May 18 to 23, 2007.

Correspondence to: Christer Sinderby, PhD, Department of Critical Care Medicine, St. Michaels's Hospital, University of Toronto, 30 Bond St, Room 4-072, Queen Wing, Toronto, ON, Canada M5B 1W8; e-mail: sinderbyc@smh.toronto.on.ca


This research was supported by St. Michael's Hospital, Toronto, ON, Canada; the Canada Foundation for Innovation; and the R. Samuel McLaughlin Foundation. Lukas Brander held postdoctoral fellowships from the Swiss Foundation for Grants in Biology and Medicine provided by Novartis AG in collaboration with the Swiss National Science Foundation, and of the Division of Respirology at the University of Toronto provided by Merck-Frosst.

The work was performed at the Department of Critical Care Medicine, St. Michael's Hospital, Toronto, ON, Canada. Drs. Beck and Sinderby have made inventions related to the neural control of mechanical ventilation that are patented. The license for these patents belongs to Maquet Critical Care. Future commercial uses of this technology may provide financial benefit to Drs. Beck and Sinderby through royalties. Drs. Beck and Sinderby each own 50% of Neurovent Research Inc. Neurovent Research Inc is a research and development company that builds the equipment and catheters for research studies. Neurovent Research Inc has a consulting agreement with Maquet Critical Care. Dr. Slutsky consults for companies that make ventilators, specifically Maquet Critical Care and Hamilton Medical, and is compensated for these consultations. Drs. Brander, Leong-Poi, Brunet, and Hutchison have reported to the ACCP that no significant 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 (www.chestjournal.org/misc/reprints.shtml).


Chest. 2009;135(3):695-703. doi:10.1378/chest.08-1747
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Background:  Neurally adjusted ventilatory assist (NAVA) delivers assist in proportion to the patient's respiratory drive as reflected by the diaphragm electrical activity (EAdi). We examined to what extent NAVA can unload inspiratory muscles, and whether unloading is sustainable when implementing a NAVA level identified as adequate (NAVAal) during a titration procedure.

Methods:  Fifteen adult, critically ill patients with a Pao2/fraction of inspired oxygen (Fio2) ratio < 300 mm Hg were studied. NAVAal was identified based on the change from a steep increase to a less steep increase in airway pressure (Paw) and tidal volume (Vt) in response to systematically increasing the NAVA level from low (NAVAlow) to high (NAVAhigh). NAVAal was implemented for 3 h.

Results:  At NAVAal, the median esophageal pressure time product (PTPes) and EAdi values were reduced by 47% of NAVAlow (quartiles, 16 to 69% of NAVAlow) and 18% of NAVAlow (quartiles, 15 to 26% of NAVAlow), respectively. At NAVAhigh, PTPes and EAdi values were reduced by 74% of NAVAlow (quartiles, 56 to 86% of NAVAlow) and 36% of NAVAlow (quartiles, 21 to 51% of NAVAlow; p ≤ 0.005 for all). Parameters during 3 h on NAVAal were not different from parameters during titration at NAVAal, and were as follows: Vt, 5.9 mL/kg predicted body weight (PBW) [quartiles, 5.4 to 7.2 mL/kg PBW]; respiratory rate (RR), 29 breaths/min (quartiles, 22 to 33 breaths/min); mean inspiratory Paw, 16 cm H2O (quartiles, 13 to 20 cm H2O); PTPes, 45% of NAVAlow (quartiles, 28 to 57% of NAVAlow); and EAdi, 76% of NAVAlow (quartiles, 63 to 89% of NAVAlow). Pao2/Fio2 ratio, Paco2, and cardiac performance during NAVAal were unchanged, while Paw and Vt were lower, and RR was higher when compared to conventional ventilation before implementing NAVAal.

Conclusions:  Systematically increasing the NAVA level reduces respiratory drive, unloads respiratory muscles, and offers a method to determine an assist level that results in sustained unloading, low Vt, and stable cardiopulmonary function when implemented for 3 h.

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