title: Establishing lung gas volumes at birth: interaction between positive end-expiratory pressures and tidal volumes in preterm rabbits.
abstract: BACKGROUND
  We investigated the effects of positive end-expiratory pressure (PEEP) and tidal volume (VT) on lung aeration, pulmonary mechanics, and the distribution of ventilation immediately after birth using a preterm rabbit model.
  
  
  METHODS
  Sixty preterm rabbits (27 d) received volume-targeted positive pressure ventilation from birth, with one of the 12 combinations of PEEP (0, 5, 8, or 10 cm H2O) and VT (4, 8, or 12 ml/kg). Outcomes included functional residual capacity (FRC), peak inflating pressure (PIP), dynamic compliance (Cd), and distribution of ventilation.
  
  
  RESULTS
  Increasing PEEP from 0 to 10 cm H2O increased FRC by 4 ml/kg, increased Cd by 0.2 ml/kg/cm H2O, and reduced PIP by 5 cm H2O. Increasing VT from 4 to 12 ml/kg increased FRC by 2 ml/kg, increased Cd by 0.3 ml/kg/cm H2O, and increased PIP by 4 cmH2O. No effect of VT on FRC occurred at 0 or 5 PEEP, and no effect of PEEP occurred at VT = 4 ml/kg. At 0 PEEP, increasing VT increased the proportion of gas entering the smaller apical regions, whereas at 10 PEEP, increasing VT increased the proportion of gas entering basal regions, from 47% to 63%.
  
  
  CONCLUSIONS
  Both PEEP and VT have independent, additive effects on FRC, lung mechanics, and the distribution of ventilation during the immediate newborn period.
authors.affiliation: The Ritchie Centre, Monash Institute for Medical Research, Monash University, Melbourne, Australia. kevin.wheeler@dhhs.tas.gov.au
authors.forename: Kevin
authors.initials: K
authors.lastname: Wheeler
authors.forename: Megan
authors.initials: M
authors.lastname: Wallace
authors.forename: Marcus
authors.initials: M
authors.lastname: Kitchen
authors.forename: Arjan
authors.initials: A
authors.lastname: Te Pas
authors.forename: Andreas
authors.initials: A
authors.lastname: Fouras
authors.forename: Muhammad
authors.initials: M
authors.lastname: Islam
authors.forename: Melissa
authors.initials: M
authors.lastname: Siew
authors.forename: Robert
authors.initials: R
authors.lastname: Lewis
authors.forename: Colin
authors.initials: C
authors.lastname: Morley
authors.forename: Peter
authors.initials: P
authors.lastname: Davis
authors.forename: Stuart
authors.initials: S
authors.lastname: Hooper
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D008168:Lung / Q000503:physiopathology*; D010100:Oxygen / Q000378:metabolism*; D011175:Positive-Pressure Respiration; D011817:Rabbits; D013990:Tidal Volume; D014109:Total Lung Capacity
chemical_list: D010100:Oxygen