title: Computed tomography scan assessment of lung volume and recruitment during high-frequency oscillatory ventilation.
abstract: OBJECTIVE
  This review describes how computed tomography has increased our understanding of the pathophysiology of acute respiratory distress syndrome. It summarizes current knowledge about lung volume changes and alveolar recruitment during high-frequency oscillatory ventilation (HFOV) assessed by computed tomography (CT), outlines potential problems when comparing HFOV with conventional ventilation (CV) as a result of the different pressure-time profiles, and describes future research directions.
  
  
  METHODS
  CT allows accurate assessment of total lung volumes and differentiation between overinflated, normally aerated, poorly aerated, and nonaerated lung regions. It allows for classification of different patterns of consolidation and may be predictive for the potential for recruitment.
  
  
  METHODS
  Experimental data suggest that HFOV at mean airway pressures (mPaw) set according to a static PV curve leads to effective lung recruitment but results in overall lung volumes that are considerably higher than those predicted from the PV relationship. In saline-lavaged sheep, similar changes in total lung volumes and subvolumes were observed during HFOV and CV. One single study specifically assessed lung volume recruitment during HFOV as compared with CV in eight patients with acute respiratory distress syndrome from pneumonia or sepsis. After 48 hrs on HFOV, total ventilated lung volume was significantly increased, whereas only a minor increase in overinflated lung volume was observed. These changes correlated with a significant improvement in gas exchange.
  
  
  CONCLUSIONS
  CT is a valuable tool to quantify recruitment and overinflation during HFOV. Additional studies are needed to better characterize the specific effects of HFOV on lung volume and morphology.
authors.affiliation: Department of Anesthesiology, University Hospital of Mannheim, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Luecke
authors.forename: Peter
authors.initials: P
authors.lastname: Herrmann
authors.forename: Paul
authors.initials: P
authors.lastname: Kraincuk
authors.forename: Paolo
authors.initials: P
authors.lastname: Pelosi
mesh_terms: D000818:Animals; D006612:High-Frequency Ventilation; D006801:Humans; D008176:Lung Volume Measurements / Q000379:methods*; D011650:Pulmonary Alveoli / Q000503:physiopathology; D012128:Respiratory Distress Syndrome / Q000503:physiopathology*; D012756:Sheep; D014057:Tomography, X-Ray Computed