title: Stress and strain within the lung.
abstract: OBJECTIVE
  To describe the physiological meaning and the clinical application of the lung stress and strain concepts.
  
  
  RESULTS
  The end-inspiratory plateau pressure and ratio of tidal volume/ideal body weight are inadequate surrogates for the end-inspiratory stress (equal to the transpulmonary pressure) and the end-inspiratory strain (change in lung volume relative to the resting volume). For a given plateau pressure or tidal volume/ideal body weight, stress and strain may vary largely due to the variability of chest wall elastance and the resting lung volume. The injurious limits of stress and strain in healthy lungs are reached when stress and strain reach the total lung capacity. This occurs when the resting lung volume (the baby lung in case of acute respiratory distress syndrome) is increased by two-fold to three-fold. As these limits are rarely reached in clinical practice and damage has been reported with stress and strain well below this upper limit, this implies the presence in the lung parenchyma of regions which act as stress raisers or pressure multipliers. These are primarily linked to the inhomogeneous distribution of local stress and strain.
  
  
  CONCLUSIONS
  End-inspiratory stress and strain, as well as the lung inhomogeneity and the stress raisers, must be taken in account when setting mechanical ventilation.
authors.affiliation: Dipartimento di Anestesiologia, Terapia Intensiva e Scienze Dermatologiche, Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy. gattinon@policlinico.mi.it
authors.forename: Luciano
authors.initials: L
authors.lastname: Gattinoni
authors.forename: Eleonora
authors.initials: E
authors.lastname: Carlesso
authors.forename: Pietro
authors.initials: P
authors.lastname: Caironi
mesh_terms: D000403:Airway Resistance; D000465:Algorithms; D001835:Body Weight; D006801:Humans; D008170:Lung Compliance; D012121:Respiration, Artificial / Q000009:adverse effects* / Q000379:methods; D013990:Tidal Volume; D014109:Total Lung Capacity; D055397:Ventilator-Induced Lung Injury / Q000401:mortality / Q000503:physiopathology*