title: Comparison of static end-expiratory and effective lung volumes for gas exchange in healthy and surfactant-depleted lungs.
abstract: BACKGROUND
  Effective lung volume (ELV) for gas exchange is a new measure that could be used as a real-time guide during controlled mechanical ventilation. The authors established the relationships of ELV to static end-expiratory lung volume (EELV) with varying levels of positive end-expiratory pressure (PEEP) in healthy and surfactant-depleted rabbit lungs.
  
  
  METHODS
  Nine rabbits were anesthetized and ventilated with a modified volume-controlled mode where periods of five consecutive alterations in inspiratory/expiratory ratio (1:2-1.5:1) were imposed to measure ELV from the corresponding carbon dioxide elimination traces. EELV and the lung clearance index were concomitantly determined by helium wash-out technique. Airway and tissue mechanics were assessed by using low-frequency forced oscillations. Measurements were collected at PEEP 0, 3, 6, and 9 cm H2O levels under control condition and after surfactant depletion by whole-lung lavage.
  
  
  RESULTS
  ELV was greater than EELV at all PEEP levels before lavage, whereas there was no evidence for a difference in the lung volume indices after surfactant depletion at PEEP 6 or 9 cm H2O. Increasing PEEP level caused significant parallel increases in both ELV and EELV levels, decreases in ventilation heterogeneity, and improvement in airway and tissue mechanics under control condition and after surfactant depletion. ELV and EELV exhibited strong and statistically significant correlations before (r=0.84) and after lavage (r=0.87).
  
  
  CONCLUSIONS
  The parallel changes in ELV and EELV with PEEP in healthy and surfactant-depleted lungs support the clinical value of ELV measurement as a bedside tool to estimate dynamic changes in EELV in children and infants.
authors.affiliation: Department of Anesthesiology, Pharmacology and Intensive Care, University of Geneva, Geneva, Switzerland.
authors.forename: Gergely
authors.initials: G
authors.lastname: Albu
authors.forename: Mats
authors.initials: M
authors.lastname: Wallin
authors.forename: Magnus
authors.initials: M
authors.lastname: Hallbäck
authors.forename: Per
authors.initials: P
authors.lastname: Emtell
authors.forename: Andrew
authors.initials: A
authors.lastname: Wolf
authors.forename: Per-Arne
authors.initials: PA
authors.lastname: Lönnqvist
authors.forename: Sylvia
authors.initials: S
authors.lastname: Göthberg
authors.forename: Ferenc
authors.initials: F
authors.lastname: Peták
authors.forename: Walid
authors.initials: W
authors.lastname: Habre
mesh_terms: D000465:Algorithms; D000704:Analysis of Variance; D000818:Animals; D006371:Helium; D006439:Hemodynamics / Q000502:physiology; D008168:Lung / Q000502:physiology*; D008176:Lung Volume Measurements; D009079:Mucociliary Clearance; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D011663:Pulmonary Surfactants / Q000378:metabolism*; D011817:Rabbits; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology
chemical_list: D011663:Pulmonary Surfactants; D006371:Helium