title: Intrinsic positive end-expiratory pressure in Acute Respiratory Distress Syndrome (ARDS) Network subjects.
abstract: OBJECTIVE
  We tested the hypothesis that subjects randomized to the 6 mL/kg predicted body weight tidal volume study group of the National Institutes of Health Acute Respiratory Distress Syndrome (ARDS) Network study had higher levels of intrinsic positive end-expiratory pressure (PEEP) than subjects randomized to the 12 mL/kg predicted body weight tidal volume study group.
  
  
  METHODS
  Secondary analysis of a subgroup from a randomized controlled trial.
  
  
  METHODS
  Hospitals located in San Francisco, CA, and Seattle, WA.
  
  
  METHODS
  Eighty-four patients enrolled in the ARDS Network tidal volume trial in San Francisco, CA, and Seattle, WA, with records of measurement of intrinsic PEEP.
  
  
  METHODS
  None.
  
  
  RESULTS
  Intrinsic PEEP was assessed a median of six times over the first 48 hrs of ARDS Network protocol ventilation in study subjects, with no significant difference in number of measurements between subjects randomized to the tidal volume protocol of 6 mL/kg compared with 12 mL/kg. We found that intrinsic PEEP was higher among subjects randomized to the 6 mL/kg protocol, with a median intrinsic PEEP of 1.3 cm H2O (interquartile range, 0-3.1 cm H2O), compared with a median intrinsic PEEP of 0.5 cm H2O (interquartile range, 0-1.5 cm H2O) among subjects randomized to 12 mL/kg (p = .029). There was no difference in total PEEP between the study groups.
  
  
  CONCLUSIONS
  In a subgroup of ARDS Network subjects, intrinsic PEEP was statistically significantly higher in subjects randomized to the 6 mL/kg protocol than those in the 12 mL/kg study group. The amount of intrinsic PEEP was very low in both study groups, and difference of median intrinsic PEEP between the groups was <1 cm H2O. It is unlikely that the difference in intrinsic PEEP between the study groups was clinically important in the ARDS Network study of low tidal volume ventilation.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine at the University of Washington, Seattle, WA, USA.
authors.forename: Catherine Lee
authors.initials: CL
authors.lastname: Hough
authors.forename: Richard H
authors.initials: RH
authors.lastname: Kallet
authors.forename: V Marco
authors.initials: VM
authors.lastname: Ranieri
authors.forename: Gordon D
authors.initials: GD
authors.lastname: Rubenfeld
authors.forename: John M
authors.initials: JM
authors.lastname: Luce
authors.forename: Leonard D
authors.initials: LD
authors.lastname: Hudson
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D008297:Male; D018467:Positive-Pressure Respiration, Intrinsic; D016032:Randomized Controlled Trials as Topic; D012121:Respiration, Artificial / Q000379:methods*; D012128:Respiratory Distress Syndrome / Q000503:physiopathology / Q000628:therapy*; D018709:Statistics, Nonparametric; D013990:Tidal Volume