title: Airway pressure release ventilation reduces conducting airway micro-strain in lung injury.
abstract: BACKGROUND
  Improper mechanical ventilation can exacerbate acute lung damage, causing a secondary ventilator-induced lung injury (VILI). We hypothesized that VILI can be reduced by modifying specific components of the ventilation waveform (mechanical breath), and we studied the impact of airway pressure release ventilation (APRV) and controlled mandatory ventilation (CMV) on the lung micro-anatomy (alveoli and conducting airways). The distribution of gas during inspiration and expiration and the strain generated during mechanical ventilation in the micro-anatomy (micro-strain) were calculated.
  
  
  METHODS
  Rats were anesthetized, surgically prepared, and randomized into 1 uninjured control group (n = 2) and 4 groups with lung injury: APRV 75% (n = 2), time at expiration (TLow) set to terminate appropriately at 75% of peak expiratory flow rate (PEFR); APRV 10% (n = 2), TLow set to terminate inappropriately at 10% of PEFR; CMV with PEEP 5 cm H2O (PEEP 5; n = 2); or PEEP 16 cm H2O (PEEP 16; n = 2). Lung injury was induced in the experimental groups by Tween lavage and ventilated with their respective settings. Lungs were fixed at peak inspiration and end expiration for standard histology. Conducting airway and alveolar air space areas were quantified and conducting airway micro-strain was calculated.
  
  
  RESULTS
  All lung injury groups redistributed inspired gas away from alveoli into the conducting airways. The APRV 75% minimized gas redistribution and micro-strain in the conducting airways and provided the alveolar air space occupancy most similar to control at both inspiration and expiration.
  
  
  CONCLUSIONS
  In an injured lung, APRV 75% maintained micro-anatomic gas distribution similar to that of the normal lung. The lung protection demonstrated in previous studies using APRV 75% may be due to a more homogeneous distribution of gas at the micro-anatomic level as well as a reduction in conducting airway micro-strain.
authors.affiliation: Department of General Surgery, SUNY Upstate Medical University, Syracuse, NY.
authors.forename: Michaela
authors.initials: M
authors.lastname: Kollisch-Singule
authors.affiliation: Department of General Surgery, SUNY Upstate Medical University, Syracuse, NY.
authors.forename: Bryanna
authors.initials: B
authors.lastname: Emr
authors.affiliation: Department of Medicine, University of Vermont, Burlington, VT.
authors.forename: Bradford
authors.initials: B
authors.lastname: Smith
authors.affiliation: Department of Biological Sciences, SUNY Cortland, Cortland, NY.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Ruiz
authors.affiliation: Department of General Surgery, SUNY Upstate Medical University, Syracuse, NY.
authors.forename: Shreyas
authors.initials: S
authors.lastname: Roy
authors.affiliation: Department of General Surgery, SUNY Upstate Medical University, Syracuse, NY.
authors.forename: Qinghe
authors.initials: Q
authors.lastname: Meng
authors.affiliation: Department of General Surgery, SUNY Upstate Medical University, Syracuse, NY.
authors.forename: Sumeet
authors.initials: S
authors.lastname: Jain
authors.affiliation: Department of General Surgery, SUNY Upstate Medical University, Syracuse, NY. Electronic address: satalinj@upstate.edu.
authors.forename: Joshua
authors.initials: J
authors.lastname: Satalin
authors.affiliation: Department of General Surgery, SUNY Upstate Medical University, Syracuse, NY.
authors.forename: Kathy
authors.initials: K
authors.lastname: Snyder
authors.affiliation: Department of General Surgery, SUNY Upstate Medical University, Syracuse, NY.
authors.forename: Auyon
authors.initials: A
authors.lastname: Ghosh
authors.affiliation: Department of General Surgery, SUNY Upstate Medical University, Syracuse, NY.
authors.forename: William H
authors.initials: WH
authors.lastname: Marx
authors.affiliation: R Adams Cowley Shock Trauma Center, Trauma Critical Care Medicine, University of Maryland School of Medicine, Baltimore, MD.
authors.forename: Penny
authors.initials: P
authors.lastname: Andrews
authors.affiliation: R Adams Cowley Shock Trauma Center, Trauma Critical Care Medicine, University of Maryland School of Medicine, Baltimore, MD.
authors.forename: Nader
authors.initials: N
authors.lastname: Habashi
authors.affiliation: Department of General Surgery, SUNY Upstate Medical University, Syracuse, NY.
authors.forename: Gary F
authors.initials: GF
authors.lastname: Nieman
authors.affiliation: Department of General Surgery, SUNY Upstate Medical University, Syracuse, NY; Department of Biological Sciences, SUNY Cortland, Cortland, NY.
authors.forename: Louis A
authors.initials: LA
authors.lastname: Gatto
mesh_terms: D000818:Animals; D008297:Male; D011650:Pulmonary Alveoli / Q000473:pathology / Q000503:physiopathology; D011659:Pulmonary Gas Exchange; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012121:Respiration, Artificial / Q000009:adverse effects / Q000379:methods*; D055397:Ventilator-Induced Lung Injury / Q000209:etiology / Q000517:prevention & control*