title: Cardiorespiratory effects of spontaneous breathing in two different models of experimental lung injury: a randomized controlled trial.
abstract: BACKGROUND
  Acute lung injury (ALI) can result from various insults to the pulmonary tissue. Experimental and clinical data suggest that spontaneous breathing (SB) during pressure-controlled ventilation (PCV) in ALI results in better lung aeration and improved oxygenation. Our objective was to evaluate whether the addition of SB has different effects in two different models of ALI.
  
  
  METHODS
  Forty-four pigs were randomly assigned to ALI resulting either from hydrochloric acid aspiration (HCl-ALI) or from increased intra-abdominal pressure plus intravenous oleic acid injections (OA-ALI) and were ventilated in PCV mode either with SB (PCV + SB) or without SB (PCV - SB). Cardiorespiratory variables were measured at baseline after induction of ALI and after 4 hours of treatment (PCV + SB or PCV - SB). Finally, density distributions and end-expiratory lung volume (EELV) were assessed by thoracic spiral computed tomography.
  
  
  RESULTS
  PCV + SB improved arterial partial pressure of oxygen/inspiratory fraction of oxygen (PaO2/FiO2) by a reduction in intrapulmonary shunt fraction in HCl-ALI from 27% +/- 6% to 23% +/- 13% and in OA-ALI from 33% +/- 19% to 26% +/- 18%, whereas during PCV - SB PaO2/FiO2 deteriorated and shunt fraction increased in the HCl group from 28% +/- 8% to 37% +/- 17% and in the OA group from 32% +/- 12% to 47% +/- 17% (P < 0.05 for interaction time and treatment, but not ALI type). PCV + SB also resulted in higher EELV (HCl-ALI: 606 +/- 171 mL, OA-ALI: 439 +/- 90 mL) as compared with PCV - SB (HCl-ALI: 372 +/- 130 mL, OA-ALI: 192 +/- 51 mL, with P < 0.05 for interaction of time, treatment, and ALI type).
  
  
  CONCLUSIONS
  SB improves oxygenation, reduces shunt fraction, and increases EELV in both models of ALI.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, University of Bonn, Sigmund-Freud-Strasse 25, D-53105 Bonn, Germany. dirk.varelmann@uni-bonn.de
authors.forename: Dirk
authors.initials: D
authors.lastname: Varelmann
authors.forename: Thomas
authors.initials: T
authors.lastname: Muders
authors.forename: Jörg
authors.initials: J
authors.lastname: Zinserling
authors.forename: Ulf
authors.initials: U
authors.lastname: Guenther
authors.forename: Anders
authors.initials: A
authors.lastname: Magnusson
authors.forename: Göran
authors.initials: G
authors.lastname: Hedenstierna
authors.forename: Christian
authors.initials: C
authors.lastname: Putensen
authors.forename: Hermann
authors.initials: H
authors.lastname: Wrigge
mesh_terms: D055371:Acute Lung Injury / Q000139:chemically induced*; D000818:Animals; D045422:Continuous Positive Airway Pressure / Q000379:methods; D023421:Models, Animal; D010101:Oxygen Consumption / Q000502:physiology; D011897:Random Allocation; D012119:Respiration; D015656:Respiratory Mechanics / Q000502:physiology*; D013548:Sweden; D013552:Swine