title: Moderate tidal volumes and oxygen exposure during initiation of ventilation in preterm fetal sheep.
abstract: BACKGROUND
  Preterm infants often receive mechanical ventilation and oxygen at birth. Exposure to large tidal volumes (V(T)s) at birth causes lung inflammation, and oxygen may amplify the injury. We hypothesized that normal V(T) ventilation at birth causes lung injury that is exacerbated by 95% oxygen.
  
  
  METHODS
  The head and chest of anesthetized preterm fetal sheep (129 ± 1 d gestation) were surgically exteriorized while maintaining the placental circulation. Fetuses were randomized to four groups with either V(T) ventilation to 6 ml/kg or continuous positive airway pressure of 5 cm H2O, and either 95%O2/5%CO2 or 95%N2/5%CO2. Age-matched fetuses were used as controls. After a 15-min intervention, the fetal lamb was returned to the uterus for 1 h 45 min.
  
  
  RESULTS
  In ventilated lambs, V(T) was 6.2 ± 0.4 ml/kg at 15 min. Ventilation increased proinflammatory cytokines as compared with controls and lambs on continuous positive airway pressure, with recruitment of primarily monocytes to bronchoalveolar lavage fluid. Early response protein 1 was activated around the bronchioles in V(T)-ventilated animals. The 15-min oxygen exposure did not change inflammatory mediators or other markers of lung and oxidative stress.
  
  
  CONCLUSIONS
  A V(T) of 6-7 ml/kg at birth increased early markers of injury and lung inflammation. Brief exposure to 95% oxygen did not alter lung inflammation.
authors.affiliation: Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Ohio, USA. Noah.Hillman@cchmc.org
authors.forename: Noah H
authors.initials: NH
authors.lastname: Hillman
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Moss
authors.forename: Ilias
authors.initials: I
authors.lastname: Nitsos
authors.forename: Alan H
authors.initials: AH
authors.lastname: Jobe
mesh_terms: D000818:Animals; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012121:Respiration, Artificial; D012756:Sheep; D013990:Tidal Volume
chemical_list: D010100:Oxygen