title: Relationship between regional lung compliance and ventilation homogeneity in the supine and prone position.
abstract: BACKGROUND
  The prone position (PP) improves ventilation homogeneity in acute respiratory distress syndrome. The aim of this study was to investigate whether the alleviation of ventilation inhomogeneity in PP was due to changes in regional lung compliance.
  
  
  METHODS
  Ten lung-lavaged piglets were mechanically ventilated in supine position (SP) and in PP. In each position, positive end-expiratory pressure (PEEP) was reduced from 20 to 6 cmH(2)O in steps of 2 cmH(2)O every 10 min after full lung recruitment. Respiratory mechanics, blood gas, haemodynamic data and whole-lung computed tomography scans were recorded at each PEEP. The compliances of normally aerated (C(normal)) and newly recruited (C(recruited)) lung regions were calculated. Open lung PEEP (OL-PEEP) was defined as the lowest PEEP to maintain full lung recruitment.
  
  
  RESULTS
  At OL-PEEP, PP significantly increased normally aerated lung regions, decreased poorly aerated and hyperinflated lung regions and decreased tidal recruitment and hyperinflation. C(normal) was significantly reduced in PP compared with SP (12.8 ± 4.2 ml/cmH(2)O vs. 20.1 ± 6.2 ml/cmH(2)O, P < 0.001), whereas C(recruited) was increased in PP (13.9 ± 3.9 ml/cmH(2)O vs. 9.4 ± 2.4 ml/cmH(2)O, P < 0.001). C(normal) was correlated with hyperinflated lung regions at end-expiration (rho = 0.67) and end-inspiration (rho = 0.56) at OL-PEEP. C(recruited) was correlated with normally (r(2) = 0.36) and poorly aerated lung regions (rho = -0.58) at OL-PEEP.
  
  
  CONCLUSIONS
  This surfactant-depleted model shows that the improvement of ventilation homogeneity in PP is related to an increase in C(recruited) and a decrease in C(normal).
authors: Department of Critical Care Medicine, Zhong-Da Hospital, School of Medicine Southeast University, Nanjing, China.
authors: R
authors: R
authors: Tang
authors: Y
authors: Y
authors: Huang
authors: Q
authors: Q
authors: Chen
authors: X
authors: X
authors: Hui
authors: Y
authors: Y
authors: Li
authors: Q
authors: Q
authors: Yu
authors: H
authors: H
authors: Zhao
authors: Y
authors: Y
authors: Yang
authors: H
authors: H
authors: Qiu
mesh_terms: D055371:Acute Lung Injury / Q000503:physiopathology; D000818:Animals; D062186:Arterial Pressure / Q000502:physiology; D002496:Central Venous Pressure / Q000502:physiology; D005260:Female; D007091:Image Processing, Computer-Assisted; D008168:Lung / Q000033:anatomy & histology / Q000502:physiology; D008170:Lung Compliance / Q000502:physiology*; D008297:Male; D010100:Oxygen / Q000097:blood; D011175:Positive-Pressure Respiration; D016684:Prone Position / Q000502:physiology*; D011651:Pulmonary Artery / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000502:physiology; D015656:Respiratory Mechanics; D016683:Supine Position / Q000502:physiology*; D013552:Swine; D013990:Tidal Volume / Q000502:physiology; D014057:Tomography, X-Ray Computed
chemical_list: D010100:Oxygen