title: Lung inhomogeneities and time course of ventilator-induced mechanical injuries.
abstract: BACKGROUND
  During mechanical ventilation, stress and strain may be locally multiplied in an inhomogeneous lung. The authors investigated whether, in healthy lungs, during high pressure/volume ventilation, injury begins at the interface of naturally inhomogeneous structures as visceral pleura, bronchi, vessels, and alveoli. The authors wished also to characterize the nature of the lesions (collapse vs. consolidation).
  
  
  METHODS
  Twelve piglets were ventilated with strain greater than 2.5 (tidal volume/end-expiratory lung volume) until whole lung edema developed. At least every 3 h, the authors acquired end-expiratory/end-inspiratory computed tomography scans to identify the site and the number of new lesions. Lung inhomogeneities and recruitability were quantified.
  
  
  RESULTS
  The first new densities developed after 8.4 ± 6.3 h (mean ± SD), and their number increased exponentially up to 15 ± 12 h. Afterward, they merged into full lung edema. A median of 61% (interquartile range, 57 to 76) of the lesions appeared in subpleural regions, 19% (interquartile range, 11 to 23) were peribronchial, and 19% (interquartile range, 6 to 25) were parenchymal (P < 0.0001). All the new densities were fully recruitable. Lung elastance and gas exchange deteriorated significantly after 18 ± 11 h, whereas lung edema developed after 20 ± 11 h.
  
  
  CONCLUSIONS
  Most of the computed tomography scan new densities developed in nonhomogeneous lung regions. The damage in this model was primarily located in the interstitial space, causing alveolar collapse and consequent high recruitability.
authors.affiliation: From the Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Fondazione IRCCS Ca' Granda-Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy (M.C., C.C., M.G., M.A., M.B., I.A., A. Cammaroto, C.R., D.M., C.B.d.C., K.N., C.M., E.C.); Dipartimento di Radiologia, Fondazione IRCCS Ca' Granda-Ospedale Maggiore Policlinico, Milan, Italy (M.L.); Centro di Ricerche Precliniche, Fondazione IRCCS Ca' Granda-Ospedale Maggiore Policlinico, Milan, Italy (D.D., S.G.); Dipartimento di Anestesia, Rianimazione ed Emergenza Urgenza, Fondazione IRCCS Ca' Granda-Ospedale Maggiore Policlinico, Milan, Italy (A. Colombo, L.G.); and Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano, Milan, Italy (V.V., N.G.).
authors.forename: Massimo
authors.initials: M
authors.lastname: Cressoni
authors.forename: Chiara
authors.initials: C
authors.lastname: Chiurazzi
authors.forename: Miriam
authors.initials: M
authors.lastname: Gotti
authors.forename: Martina
authors.initials: M
authors.lastname: Amini
authors.forename: Matteo
authors.initials: M
authors.lastname: Brioni
authors.forename: Ilaria
authors.initials: I
authors.lastname: Algieri
authors.forename: Antonio
authors.initials: A
authors.lastname: Cammaroto
authors.forename: Cristina
authors.initials: C
authors.lastname: Rovati
authors.forename: Dario
authors.initials: D
authors.lastname: Massari
authors.forename: Caterina Bacile
authors.initials: CB
authors.lastname: di Castiglione
authors.forename: Klodiana
authors.initials: K
authors.lastname: Nikolla
authors.forename: Claudia
authors.initials: C
authors.lastname: Montaruli
authors.forename: Marco
authors.initials: M
authors.lastname: Lazzerini
authors.forename: Daniele
authors.initials: D
authors.lastname: Dondossola
authors.forename: Angelo
authors.initials: A
authors.lastname: Colombo
authors.forename: Stefano
authors.initials: S
authors.lastname: Gatti
authors.forename: Vincenza
authors.initials: V
authors.lastname: Valerio
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Gagliano
authors.forename: Eleonora
authors.initials: E
authors.lastname: Carlesso
authors.forename: Luciano
authors.initials: L
authors.lastname: Gattinoni
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D005260:Female; D008168:Lung / Q000473:pathology*; D012121:Respiration, Artificial / Q000009:adverse effects* / Q000639:trends; D013552:Swine; D013997:Time Factors; D055397:Ventilator-Induced Lung Injury / Q000209:etiology* / Q000473:pathology*; D012122:Ventilators, Mechanical / Q000009:adverse effects* / Q000639:trends