title: Roles of neurally adjusted ventilatory assist in improving gas exchange in a severe acute respiratory distress syndrome patient after weaning from extracorporeal membrane oxygenation: a case report.
abstract: BACKGROUND
  Patient-ventilator asynchrony is a major cause of difficult weaning from mechanical ventilation. Neurally adjusted ventilatory assist (NAVA) is reported useful to improve the synchrony in patients with sustained low lung compliance. However, the role of NAVA has not been fully investigated.
  
  
  METHODS
  The patient was a 63-year-old Japanese man with acute respiratory distress syndrome secondary to respiratory infection. He was treated with extracorporeal membrane oxygenation for 7 days and survived. Dynamic compliance at withdrawal of extracorporeal membrane oxygenation decreased to 20 ml/cmH2O or less, but gas exchange was maintained by full support with assist/control mode. However, weaning from mechanical ventilation using a flow trigger failed repeatedly because of patient-ventilator asynchrony with hypercapnic acidosis during partial ventilator support despite using different types of ventilators and different trigger levels. Weaning using NAVA restored the regular respiration and stable and normal acid-base balance. Electromyographic analysis of the diaphragm clearly showed improved triggering of both the start and the end of spontaneous inspiration. Regional ventilation monitoring using electrical impedance tomography showed an increase in tidal volume and a ventilation shift to the dorsal regions during NAVA, indicating that NAVA could deliver gas flow to the dorsal regions to adjust for the magnitude of diaphragmatic excursion. NAVA was applied for 31 days, followed by partial ventilatory support with a conventional flow trigger. The patient was discharged from the intensive care unit on day 110 and has recovered enough to be able to live without a ventilatory support for 5 h per day.
  
  
  CONCLUSIONS
  Our experience showed that NAVA improved not only patient-ventilator synchrony but also regional ventilation distribution in an acute respiratory distress patient with sustained low lung compliance.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Tokyo Women's Medical University, Tokyo, 162-8666 Japan.
authors.forename: Yuya
authors.initials: Y
authors.lastname: Goto
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Tokyo Women's Medical University, Tokyo, 162-8666 Japan.
authors.forename: Shinshu
authors.initials: S
authors.lastname: Katayama
authors.affiliation: Department of Anesthesiology, Shimane University, Shimane, 693-8501 Japan.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Shono
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Tokyo Women's Medical University, Tokyo, 162-8666 Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Mori
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Tokyo Women's Medical University, Tokyo, 162-8666 Japan.
authors.forename: Yuya
authors.initials: Y
authors.lastname: Miyazaki
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Tokyo Women's Medical University, Tokyo, 162-8666 Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Sato
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Tokyo Women's Medical University, Tokyo, 162-8666 Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Ozaki
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Tokyo Women's Medical University, Tokyo, 162-8666 Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Kotani
keywords: Compliance; Electrical impedance tomography; Electromyography; Neurally adjusted ventilatory assist; Patient-ventilator synchrony; Ventilation distribution