title: Which is the most important strain in the pathogenesis of ventilator-induced lung injury: dynamic or static?
abstract: OBJECTIVE
  To discuss the relative role of dynamic and static tissue deformation (strain) generated by inflation of tidal volume and application of positive end-expiratory pressure in the pathogenesis of ventilator-induced lung injury.
  
  
  RESULTS
  Cellular, animal and human studies strongly suggest that dynamic strain is more injurious than static strain, at least when total lung capacity is not exceeded. One possible explanation for these findings is pulmonary viscoelasticity. Large and rapid dynamic deformations generate high and unevenly distributed tensions, internal frictions and energy dissipation in the form of heat, posing microstructure at risk for rupture. The most important strategy to protect the lung may thus be limiting the tidal volume. Increasing static strain may add benefit by diminishing inhomogeneities (stress raisers), especially in the already severely injured lung. On the other side, however, it may adversely affect the haemodynamics.
  
  
  CONCLUSIONS
  Large lung dynamic strain is more harmful than equivalent static strain.
authors.affiliation: aDipartimento di Anestesia, Rianimazione ed Emergenza-Urgenza, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico di Milano bDipartimento di Bioingegneria, Politecnico di Milano cDipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Protti
authors.forename: Emiliano
authors.initials: E
authors.lastname: Votta
authors.forename: Luciano
authors.initials: L
authors.lastname: Gattinoni
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004548:Elasticity; D004847:Epithelial Cells / Q000473:pathology*; D006439:Hemodynamics; D006801:Humans; D008168:Lung / Q000473:pathology* / Q000503:physiopathology*; D008170:Lung Compliance; D011659:Pulmonary Gas Exchange; D051381:Rats; D012121:Respiration, Artificial / Q000009:adverse effects*; D020545:Respiratory Mucosa / Q000503:physiopathology*; D018570:Risk Assessment; D013312:Stress, Physiological; D013552:Swine; D013990:Tidal Volume; D014109:Total Lung Capacity; D055397:Ventilator-Induced Lung Injury / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology