title: Very low tidal volume ventilation with associated hypercapnia--effects on lung injury in a model for acute respiratory distress syndrome.
abstract: BACKGROUND
  Ventilation using low tidal volumes with permission of hypercapnia is recommended to protect the lung in acute respiratory distress syndrome. However, the most lung protective tidal volume in association with hypercapnia is unknown. The aim of this study was to assess the effects of different tidal volumes with associated hypercapnia on lung injury and gas exchange in a model for acute respiratory distress syndrome.
  
  
  RESULTS
  In this randomized controlled experiment sixty-four surfactant-depleted rabbits were exposed to 6 hours of mechanical ventilation with the following targets: Group 1: tidal volume = 8-10 ml/kg/PaCO(2) = 40 mm Hg; Group 2: tidal volume = 4-5 ml/kg/PaCO(2) = 80 mm Hg; Group 3: tidal volume = 3-4 ml/kg/PaCO(2) = 120 mm Hg; Group 4: tidal volume = 2-3 ml/kg/PaCO(2) = 160 mm Hg. Decreased wet-dry weight ratios of the lungs, lower histological lung injury scores and higher PaO(2) were found in all low tidal volume/hypercapnia groups (group 2, 3, 4) as compared to the group with conventional tidal volume/normocapnia (group 1). The reduction of the tidal volume below 4-5 ml/kg did not enhance lung protection. However, oxygenation and lung protection were maintained at extremely low tidal volumes in association with very severe hypercapnia and no adverse hemodynamic effects were observed with this strategy.
  
  
  CONCLUSIONS
  Ventilation with low tidal volumes and associated hypercapnia was lung protective. A tidal volume below 4-5 ml/kg/PaCO(2) 80 mm Hg with concomitant more severe hypercapnic acidosis did not increase lung protection in this surfactant deficiency model. However, even at extremely low tidal volumes in association with severe hypercapnia lung protection and oxygenation were maintained.
authors: Division of Neonatology and Pediatric Critical Care, Department of Pediatrics and Adolescent Medicine, Ulm University, Ulm, Germany. hans.fuchs@uniklinik-ulm.de
authors: Hans
authors: H
authors: Fuchs
authors: Marc R
authors: MR
authors: Mendler
authors: Dominik
authors: D
authors: Scharnbeck
authors: Michael
authors: M
authors: Ebsen
authors: Helmut D
authors: HD
authors: Hummler
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D006439:Hemodynamics; D006935:Hypercapnia / Q000150:complications*; D055370:Lung Injury / Q000209:etiology*; D010100:Oxygen; D011817:Rabbits; D012121:Respiration, Artificial / Q000009:adverse effects*; D012128:Respiratory Distress Syndrome / Q000209:etiology*; D013990:Tidal Volume
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen