title: Neuro-ventilatory efficiency during weaning from mechanical ventilation using neurally adjusted ventilatory assist.
abstract: BACKGROUND
  Neuro-ventilatory efficiency (NVE), defined as the tidal volume to electrical diaphragm-activity ratio (VT/EAdi) at the beginning and end of the weaning process after acute hypoxaemic respiratory failure, may provide valuable information about patient recovery.
  
  
  METHODS
  This observational study included 12 patients breathing with neurally adjusted ventilatory assist (NAVA). When a spontaneous breathing trial (SBT) with pressure support of 7 cm H2O and PEEP was unsuccessful, NAVA was used and the level was adjusted to obtain an EAdi of ∼60% of maximal EAdi during SBT. VT and EAdi were recorded continuously. We compared changes in NVE between NAVA and SBT at the first failed and first successful SBT.
  
  
  RESULTS
  When patients were switched from NAVA to SBT, NVE was significantly reduced during both unsuccessful and successful SBT (-56 and -38%, respectively); however, this reduction was significantly lower when SBT was successful (P=0.01). Between the first and last day of weaning, we observed that NVE decreased with NAVA [40.6 (27.7-89.5) vs 28.8 (18.6-46.7); P=0.002] with a significant decrease in NAVA level, whereas it remained unchanged during SBT [15.4 (10.7-39.1) vs 19.5 (11.6-29.6); P=0.50] with significant increases in both EAdi and VT and no difference in respiratory rhythm.
  
  
  CONCLUSIONS
  These results suggest that in patients after respiratory failure and prolonged mechanical ventilation, changes in VT and NVE, between SBTs are indicative of patient recovery. Larger clinical trials are needed to clarify whether changes in NVE reliably predict weaning in patients ventilated with NAVA.
authors: CHU de Bordeaux, Service d'Anesthésie-Réanimation II, F-33600 Pessac, France.
authors: H
authors: H
authors: Rozé
authors: B
authors: B
authors: Repusseau
authors: V
authors: V
authors: Perrier
authors: A
authors: A
authors: Germain
authors: R
authors: R
authors: Séramondi
authors: A
authors: A
authors: Dewitte
authors: C
authors: C
authors: Fleureau
authors: A
authors: A
authors: Ouattara
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003964:Diaphragm / Q000503:physiopathology; D004576:Electromyography / Q000379:methods; D006801:Humans; D059725:Interactive Ventilatory Support / Q000379:methods*; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D011379:Prognosis; D012128:Respiratory Distress Syndrome / Q000503:physiopathology / Q000628:therapy; D013990:Tidal Volume / Q000502:physiology; D015300:Ventilator Weaning / Q000379:methods*; D055815:Young Adult
keywords: mechanical ventilator weaning; neurally adjusted ventilatory assist