title: Physiologic rationale for ventilator setting in acute lung injury/acute respiratory distress syndrome patients.
abstract: OBJECTIVE
  To review the physiologic approach to setting mechanical ventilation in acute lung injury/acute respiratory distress syndrome.
  
  
  METHODS
  MEDLINE search from 1979 to the present.
  
  
  METHODS
  Personal selection of some articles we believe relevant for understanding acute lung injury/acute respiratory distress syndrome physiopathology and its physiologic management.
  
  
  METHODS
  Knowing the underlying pathology is key to estimating the potential for recruitment. The potential for recruitment is rather low when the consolidation of pulmonary units exceeds collapse, as in diffuse pneumonia. In contrast, when pulmonary unit collapse exceeds consolidation, as in acute lung injury/acute respiratory distress syndrome from extrapulmonary origin, the potential for recruitment may be high. To exploit the potential for recruitment, a transpulmonary pressure greater than the opening pressure must be applied to the lung. To do so, chest wall elastance must be measured or estimated. To avoid collapse after recruitment, a positive end-expiratory pressure greater than the compressive forces operating on the lung and an alveolar ventilation sufficient to prevent absorption atelectasis must be provided. Indeed, avoidance of stretch (low airway plateau pressure) and prevention of cyclic collapse and reopening (adequate positive end-expiratory pressure and alveolar ventilation) are the physiologic cornerstones of mechanical ventilation in acute lung injury/acute respiratory distress syndrome. When considering all the randomized clinical trials reported so far, it is tempting to speculate that transpulmonary pressure and stresses, rather than tidal volume per se, are the key factors that may have an impact on mortality.
  
  
  CONCLUSIONS
  The majority of physiologic, experimental, and clinical trial data converge on one simple concept: treat the lung gently.
authors.affiliation: Istituto di Anestesia e Rianimazione, Universita' degli Studi di Milano, Ospedale Policlinico-IRCCS, Milano, Italy.
authors.forename: Luciano
authors.initials: L
authors.lastname: Gattinoni
authors.forename: Federica
authors.initials: F
authors.lastname: Vagginelli
authors.forename: Davide
authors.initials: D
authors.lastname: Chiumello
authors.forename: Paolo
authors.initials: P
authors.lastname: Taccone
authors.forename: Eleonora
authors.initials: E
authors.lastname: Carlesso
mesh_terms: D006801:Humans; D011175:Positive-Pressure Respiration; D012121:Respiration, Artificial / Q000009:adverse effects / Q000379:methods*; D012128:Respiratory Distress Syndrome / Q000503:physiopathology* / Q000628:therapy