title: Noninvasive ventilation through a helmet in postextubation hypoxemic patients: physiologic comparison between neurally adjusted ventilatory assist and pressure support ventilation.
abstract: OBJECTIVE
  Neurally adjusted ventilatory assist (NAVA) has been shown to improve patient-ventilator interaction and reduce asynchronies in intubated patients, as opposed to pressure support ventilation (PSV). This is a short-term head-to-head physiologic comparison between PSV and NAVA in delivering noninvasive ventilation through a helmet (h-NIV), in patients with postextubation hypoxemic acute respiratory failure.
  
  
  METHODS
  Ten patients underwent three 20-min trials of h-NIV in PSV, NAVA, and PSV again. Arterial blood gases (ABGs) were assessed at the end of each trial. Diaphragm electrical activity (EAdi) and airway pressure (P                            (aw)) were recorded to derive neural and mechanical respiratory rate and timing, inspiratory (delay(TR-insp)) and expiratory trigger delays (delay(TR-exp)), time of synchrony between diaphragm contraction and ventilator assistance (time(synch)), and the asynchrony index (AI).
  
  
  RESULTS
  ABGs, peak EAdi, peak P                            (aw), respiratory rate, either neural or mechanical, neural timing, and delay(TR-exp) were not different between trials. Compared with PSV, with NAVA the mechanical expiratory time was significantly shorter, while the inspiratory time and duty cycle were greater. Time(synch) was 0.79 ± 0.35 s in NAVA versus 0.60 ± 0.30 s and 0.55 ± 0.29 s during the PSV trials (p < 0.01 for both). AI exceeded 10% during both PSV trials, while not in NAVA (p < 0.001).
  
  
  CONCLUSIONS
  Compared with PSV, NAVA improves patient-ventilator interaction and synchrony, with no difference in gas exchange, respiratory rate, and neural drive and timing.
authors: Anesthesia and Intensive Care, Maggiore della Carità University Hospital, Novara, Italy.
authors: Gianmaria
authors: G
authors: Cammarota
authors: Carlo
authors: C
authors: Olivieri
authors: Roberta
authors: R
authors: Costa
authors: Rosanna
authors: R
authors: Vaschetto
authors: Davide
authors: D
authors: Colombo
authors: Emilia
authors: E
authors: Turucz
authors: Federico
authors: F
authors: Longhini
authors: Francesco
authors: F
authors: Della Corte
authors: Giorgio
authors: G
authors: Conti
authors: Paolo
authors: P
authors: Navalesi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D060666:Airway Extubation; D001784:Blood Gas Analysis; D005260:Female; D006801:Humans; D000860:Hypoxia; D059725:Interactive Ventilatory Support / Q000295:instrumentation* / Q000379:methods; D007558:Italy; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D011175:Positive-Pressure Respiration / Q000295:instrumentation* / Q000379:methods; D012119:Respiration; D013990:Tidal Volume / Q000502:physiology; D014939:Work of Breathing / Q000502:physiology