title: Higher levels of spontaneous breathing reduce lung injury in experimental moderate acute respiratory distress syndrome.
abstract: OBJECTIVE
  To assess the effects of different levels of spontaneous breathing during biphasic positive airway pressure/airway pressure release ventilation on lung function and injury in an experimental model of moderate acute respiratory distress syndrome.
  
  
  METHODS
  Multiple-arm randomized experimental study.
  
  
  METHODS
  University hospital research facility.
  
  
  METHODS
  Thirty-six juvenile pigs.
  
  
  METHODS
  Pigs were anesthetized, intubated, and mechanically ventilated. Moderate acute respiratory distress syndrome was induced by repetitive saline lung lavage. Biphasic positive airway pressure/airway pressure release ventilation was conducted using the airway pressure release ventilation mode with an inspiratory/expiratory ratio of 1:1. Animals were randomly assigned to one of four levels of spontaneous breath in total minute ventilation (n = 9 per group, 6 hr each): 1) biphasic positive airway pressure/airway pressure release ventilation, 0%; 2) biphasic positive airway pressure/airway pressure release ventilation, > 0-30%; 3) biphasic positive airway pressure/airway pressure release ventilation, > 30-60%, and 4) biphasic positive airway pressure/airway pressure release ventilation, > 60%.
  
  
  RESULTS
  The inspiratory effort measured by the esophageal pressure time product increased proportionally to the amount of spontaneous breath and was accompanied by improvements in oxygenation and respiratory system elastance. Compared with biphasic positive airway pressure/airway pressure release ventilation of 0%, biphasic positive airway pressure/airway pressure release ventilation more than 60% resulted in lowest venous admixture, as well as peak and mean airway and transpulmonary pressures, redistributed ventilation to dependent lung regions, reduced the cumulative diffuse alveolar damage score across lungs (median [interquartile range], 11 [3-40] vs 18 [2-69]; p < 0.05), and decreased the level of tumor necrosis factor-α in ventral lung tissue (median [interquartile range], 17.7 pg/mg [8.4-19.8] vs 34.5 pg/mg [29.9-42.7]; p < 0.05). Biphasic positive airway pressure/airway pressure release ventilation more than 0-30% and more than 30-60% showed a less consistent pattern of improvement in lung function, inflammation, and damage compared with biphasic positive airway pressure/airway pressure release ventilation more than 60%.
  
  
  CONCLUSIONS
  In this model of moderate acute respiratory distress syndrome in pigs, biphasic positive airway pressure/airway pressure release ventilation with levels of spontaneous breath higher than usually seen in clinical practice, that is, more than 30% of total minute ventilation, reduced lung injury with improved respiratory function, as compared with protective controlled mechanical ventilation.
authors.affiliation: 1Department of Anesthesiology and Intensive Care Medicine, Pulmonary Engineering Group, University Hospital Dresden, Technische Universität Dresden, Dresden, Germany. 2Department of Electronic Engineering, Federal University of Minas Gerais, Belo Horizonte, Brazil. 3Institute for Medical Informatics and Biometry, Technische Universität Dresden, Dresden, Germany. 4Institute of Anatomy, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany. 5Laboratory of Pulmonary Investigation, Carlos Chagas Filho Biophysics Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.. 6Department of Surgical Sciences and Integrated Diagnostics, IRCCS San Martino Hospital, University of Genoa, Genoa, Italy.
authors.forename: Nadja C
authors.initials: NC
authors.lastname: Carvalho
authors.forename: Andreas
authors.initials: A
authors.lastname: Güldner
authors.forename: Alessandro
authors.initials: A
authors.lastname: Beda
authors.forename: Ines
authors.initials: I
authors.lastname: Rentzsch
authors.forename: Christopher
authors.initials: C
authors.lastname: Uhlig
authors.forename: Susanne
authors.initials: S
authors.lastname: Dittrich
authors.forename: Peter M
authors.initials: PM
authors.lastname: Spieth
authors.forename: Bärbel
authors.initials: B
authors.lastname: Wiedemann
authors.forename: Michael
authors.initials: M
authors.lastname: Kasper
authors.forename: Thea
authors.initials: T
authors.lastname: Koch
authors.forename: Torsten
authors.initials: T
authors.lastname: Richter
authors.forename: Patricia R
authors.initials: PR
authors.lastname: Rocco
authors.forename: Paolo
authors.initials: P
authors.lastname: Pelosi
authors.forename: Marcelo Gama
authors.initials: MG
authors.lastname: de Abreu
mesh_terms: D000818:Animals; D045422:Continuous Positive Airway Pressure / Q000379:methods; D004195:Disease Models, Animal; D006439:Hemodynamics / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology*; D011175:Positive-Pressure Respiration / Q000379:methods*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D011897:Random Allocation; D012016:Reference Values; D012119:Respiration; D012128:Respiratory Distress Syndrome / Q000503:physiopathology* / Q000628:therapy*; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics; D012720:Severity of Illness Index; D013552:Swine; D016896:Treatment Outcome; D055397:Ventilator-Induced Lung Injury / Q000517:prevention & control*