title: Ventilatory protective strategies during thoracic surgery: effects of alveolar recruitment maneuver and low-tidal volume ventilation on lung density distribution.
abstract: BACKGROUND
  The increased tidal volume (V(T)) applied to the ventilated lung during one-lung ventilation (OLV) enhances cyclic alveolar recruitment and mechanical stress. It is unknown whether alveolar recruitment maneuvers (ARMs) and reduced V(T) may influence tidal recruitment and lung density. Therefore, the effects of ARM and OLV with different V(T) on pulmonary gas/tissue distribution are examined.
  
  
  METHODS
  Eight anesthetized piglets were mechanically ventilated (V(T) = 10 ml/kg). A defined ARM was applied to the whole lung (40 cm H(2)O for 10 s). Spiral computed tomographic lung scans were acquired before and after ARM. Thereafter, the lungs were separated with an endobronchial blocker. The pigs were randomized to receive OLV in the dependent lung with a V(T) of either 5 or 10 ml/kg. Computed tomography was repeated during and after OLV. The voxels were categorized by density intervals (i.e., atelectasis, poorly aerated, normally aerated, or overaerated). Tidal recruitment was defined as the addition of gas to collapsed lung regions.
  
  
  RESULTS
  The dependent lung contained atelectatic (56 ± 10 ml), poorly aerated (183 ± 10 ml), and normally aerated (187 ± 29 ml) regions before ARM. After ARM, lung volume and aeration increased (426 ± 35 vs. 526 ± 69 ml). Respiratory compliance enhanced, and tidal recruitment decreased (95% vs. 79% of the whole end-expiratory lung volume). OLV with 10 ml/kg further increased aeration (atelectasis, 15 ± 2 ml; poorly aerated, 94 ± 24 ml; normally aerated, 580 ± 98 ml) and tidal recruitment (81% of the dependent lung). OLV with 5 ml/kg did not affect tidal recruitment or lung density distribution. (Data are given as mean ± SD.)
  
  
  CONCLUSIONS
  The ARM improves aeration and respiratory mechanics. In contrast to OLV with high V(T), OLV with reduced V(T) does not reinforce tidal recruitment, indicating decreased mechanical stress.
authors: Department of Anesthesiology and Intensive Care Medicine, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany.
authors: Alf
authors: A
authors: Kozian
authors: Thomas
authors: T
authors: Schilling
authors: Hartmut
authors: H
authors: Schütze
authors: Mert
authors: M
authors: Senturk
authors: Thomas
authors: T
authors: Hachenberg
authors: Göran
authors: G
authors: Hedenstierna
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D004195:Disease Models, Animal; D007091:Image Processing, Computer-Assisted; D008168:Lung / Q000000981:diagnostic imaging; D008170:Lung Compliance; D055370:Lung Injury / Q000517:prevention & control*; D008176:Lung Volume Measurements; D011446:Prospective Studies; D011650:Pulmonary Alveoli / Q000000981:diagnostic imaging*; D001261:Pulmonary Atelectasis / Q000000981:diagnostic imaging*; D012123:Pulmonary Ventilation; D012121:Respiration, Artificial / Q000379:methods*; D015656:Respiratory Mechanics; D013552:Swine; D019616:Thoracic Surgical Procedures; D013990:Tidal Volume; D036542:Tomography, Spiral Computed / Q000379:methods