title: Effect of positive end-expiratory pressure on regional ventilation distribution during bronchoconstriction in rabbit studied by synchrotron radiation imaging.
abstract: OBJECTIVE
  To assess the effects of positive end-expiratory pressure on regional ventilation distribution in normal lung and after histamine-induced bronchoconstriction.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  International research laboratory.
  
  
  METHODS
  Six healthy New Zealand rabbits weighing 2.5 ± 0.1 kg.
  
  
  METHODS
  Rabbits were anesthetized, tracheostomized, paralyzed, and mechanically ventilated. Synchrotron radiation computed tomography images of tissue density and specific ventilation were acquired using K-edge subtraction imaging with inhaled stable xenon gas in middle and caudal thoracic levels on 0 and 5 cm H(2)O positive end-expiratory pressure at baseline and twice after histamine inhalation.
  
  
  RESULTS
  At baseline, a positive end-expiratory pressure of 5 cm H(2)O significantly increased lung volume. Histamine inhalation caused patchy areas of decreased specific ventilation, including some areas with no ventilation. After histamine, positive end-expiratory pressure significantly increased the area of well-ventilated lung regions and decreased the heterogeneity of specific ventilation. This improvement went together with a significant but limited increase in the area of hyperinflated lung zones.
  
  
  CONCLUSIONS
  The findings of this study suggest that in mechanically ventilated rabbit with severely heterogeneous bronchoconstriction, a positive end-expiratory pressure of 5 cm H(2)O significantly improves regional ventilation homogeneity through dilation of flow-limited airways and recruitment of closed airways.
authors.affiliation: European Synchrotron Radiation Facility, Grenoble, France.
authors.forename: Liisa
authors.initials: L
authors.lastname: Porra
authors.forename: Heikki
authors.initials: H
authors.lastname: Suhonen
authors.forename: Pekka
authors.initials: P
authors.lastname: Suortti
authors.forename: Anssi R A
authors.initials: AR
authors.lastname: Sovijärvi
authors.forename: Sam
authors.initials: S
authors.lastname: Bayat
mesh_terms: D000818:Animals; D016084:Bronchoconstriction / Q000502:physiology*; D016085:Bronchoconstrictor Agents; D006632:Histamine; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008176:Lung Volume Measurements; D008297:Male; D011175:Positive-Pressure Respiration; D012123:Pulmonary Ventilation / Q000502:physiology*; D011817:Rabbits; D017356:Synchrotrons; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D016085:Bronchoconstrictor Agents; D006632:Histamine