title: VTCO2 and dynamic compliance-guided lung recruitment in surfactant-depleted piglets: a computed tomography study.
abstract: OBJECTIVE
  Using computed tomography (CT) as reference, our primary objectives were to test if maximal tidal elimination of carbon dioxide (VTCO2) could be used as a marker of "optimal recruitment," indicating maximal available lung tissue for gas exchange and if a decrease in dynamic compliance (Cdyn) indicated the beginning of lung collapse during a downward positive end-expiratory pressure (PEEP) titration.
  
  
  METHODS
  Prospective laboratory animal investigation.
  
  
  METHODS
  Clinical physiology research laboratory.
  
  
  METHODS
  Six piglets undergoing lung lavage.
  
  
  METHODS
  Saline-lavaged piglets were initially ventilated without PEEP at a tidal volume (VT) of 10 mL/kg followed by baseline ventilation at end-inspiratory pressure (EIP) 25 cm H2O and PEEP 6 cm H2O. PEEP was increased to 12 or 15 cm H2O. Then EIP was increased in steps of 5 cm H2O and the EIP where VTCO2 peaked or leveled off was assumed to define optimally recruited lungs. A downward PEEP titration followed from 12 or 15 to 4 cm H2O in steps of 1 cm H2O. First decline of Cdyn was assumed to define onset of lung collapse. VTCO2 and Cdyn were continuously recorded and CT scans iterated for each change of ventilation. "Open-lung PEEP" was set 2 cm H2O above PEEP at the first Cdyn decline and was used for a final period of "open-lung ventilation."
  
  
  RESULTS
  CT images showed recruited lungs at peak VTCO2 and that a minimal amount of normally aerated lung was added by further increase in EIP. Cdyn declined just before CT scans indicated lung collapse. Compared with baseline, the target VT of 10 mL/kg was achieved at lower EIP and pressure amplitude (EIP-PEEP) during the final open-lung ventilation with more normally aerated and fewer collapsed lungs. Cdyn was doubled after recruitment.
  
  
  CONCLUSIONS
  The lung recruitment maneuver was effective and lungs optimally recruited at maximal VTCO2. A fall in Cdyn indicated lung collapse during downward PEEP titration as confirmed by CT.
authors.affiliation: Department of Paediatric Anaesthesia and Intensive Care, The Queen Silvia Children's Hospital, University of Gothenburg, Göteborg, Sweden. angela.hanson@vgregion.se
authors.forename: Angela
authors.initials: A
authors.lastname: Hanson
authors.forename: Sylvia
authors.initials: S
authors.lastname: Göthberg
authors.forename: Krister
authors.initials: K
authors.lastname: Nilsson
authors.forename: Lars E
authors.initials: LE
authors.lastname: Larsson
authors.forename: Göran
authors.initials: G
authors.lastname: Hedenstierna
mesh_terms: D000818:Animals; D002244:Carbon / Q000378:metabolism; D008168:Lung / Q000000981:diagnostic imaging*; D008170:Lung Compliance; D011175:Positive-Pressure Respiration / Q000379:methods*; D001261:Pulmonary Atelectasis / Q000000981:diagnostic imaging / Q000517:prevention & control*; D011659:Pulmonary Gas Exchange; D013552:Swine; D014057:Tomography, X-Ray Computed
chemical_list: D002244:Carbon