title: Assisted Ventilation in Patients with Acute Respiratory Distress Syndrome: Lung-distending Pressure and Patient-Ventilator Interaction.
abstract: BACKGROUND
  In patients with acute respiratory distress syndrome (ARDS), the use of assisted mechanical ventilation is a subject of debate. Assisted ventilation has benefits over controlled ventilation, such as preserved diaphragm function and improved oxygenation. Therefore, higher level of "patient control" of ventilator assist may be preferable in ARDS. However, assisted modes may also increase the risk of high tidal volumes and lung-distending pressures. The current study aims to quantify how differences in freedom to control the ventilator affect lung-protective ventilation, breathing pattern variability, and patient-ventilator interaction.
  
  
  METHODS
  Twelve patients with ARDS were ventilated in a randomized order with assist pressure control ventilation (PCV), pressure support ventilation (PSV), and neurally adjusted ventilatory assist (NAVA). Transpulmonary pressure, tidal volume, diaphragm electrical activity, and patient-ventilator interaction were measured. Respiratory variability was assessed using the coefficient of variation of tidal volume.
  
  
  RESULTS
  During inspiration, transpulmonary pressure was slightly lower with NAVA (10.3 ± 0.7, 11.2 ± 0.7, and 9.4 ± 0.7 cm H2O for PCV, PSV, and NAVA, respectively; P < 0.01). Tidal volume was similar between modes (6.6 [5.7 to 7.0], 6.4 [5.8 to 7.0], and 6.0 [5.6 to 7.3] ml/kg for PCV, PSV, and NAVA, respectively), but respiratory variability was higher with NAVA (8.0 [6.4 to 10.0], 7.1 [5.9 to 9.0], and 17.0 [12.0 to 36.1] % for PCV, PSV, and NAVA, respectively; P < 0.001). Patient-ventilator interaction improved with NAVA (6 [5 to 8] % error) compared with PCV (29 [14 to 52] % error) and PSV (12 [9 to 27] % error); P < 0.0001.
  
  
  CONCLUSIONS
  In patients with mild-to-moderate ARDS, increasing freedom to control the ventilator maintains lung-protective ventilation in terms of tidal volume and lung-distending pressure, but it improves patient-ventilator interaction and preserves respiratory variability.
authors.affiliation: From the Department of Critical Care Medicine, Radboud University Medical Center, Nijmegen, The Netherlands (J.D., J.G.v.d.H., L.M.A.H.); Department of Critical Care Medicine, St. Michael's Hospital, Toronto, Ontario, Canada (C.A.S.); Department of Pediatrics, University of Toronto, Toronto, Ontario, Canada (J.B.); and Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, Ontario, Canada (C.A.S., J.B.).
authors.forename: Jonne
authors.initials: J
authors.lastname: Doorduin
authors.forename: Christer A
authors.initials: CA
authors.lastname: Sinderby
authors.forename: Jennifer
authors.initials: J
authors.lastname: Beck
authors.forename: Johannes G
authors.initials: JG
authors.lastname: van der Hoeven
authors.forename: Leo M A
authors.initials: LM
authors.lastname: Heunks
mesh_terms: D000368:Aged; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D008168:Lung / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010358:Patient Participation / Q000379:methods*; D011897:Random Allocation; D012121:Respiration, Artificial / Q000379:methods*; D012128:Respiratory Distress Syndrome / Q000503:physiopathology / Q000628:therapy*; D012648:Self Care / Q000379:methods*; D012122:Ventilators, Mechanical / Q000592:standards