title: Assessing gas exchange in acute lung injury/acute respiratory distress syndrome: diagnostic techniques and prognostic relevance.
abstract: OBJECTIVE
  To provide the most recent insights on the assessment of gas exchange in acute lung injury.
  
  
  RESULTS
  Central venous blood may be used as a surrogate of arterial blood to assess carbon dioxide tension and acid-base status. In contrast arterial oxygenation cannot be estimated with confidence from venous blood. However, the use of venous blood associated with pulse oximetry may provide the SvO2 which is useful for monitoring and targeting the resuscitation therapy. Impaired CO2 clearance and increased dead space have been confirmed as useful prognostic indices of structural lung damage and mortality in acute respiratory failure. A simplified technique based on multiple inert gas technique has been described to assess ventilation-perfusion mismatch while a new analysis of pulse oximetry has been suggested to detect lung opening and closing. Finally, new insight has been provided on the relationship between lung anatomy, as detected by computed tomography, oxygenation and CO2 clearance.
  
  
  CONCLUSIONS
  Although oxygenation assessment is of primary importance during respiratory lung injury, dead space and CO2 retention are more strictly associated with outcome. The association of central venous blood analysis and pulse oximetry may provide more information than arterial blood alone.
authors.affiliation: Dipartimento di Anestesia, Rianimazione (Intensiva e Subintensiva) e Terapia del Dolore, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico di Milano, 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: Massimo
authors.initials: M
authors.lastname: Cressoni
mesh_terms: D055371:Acute Lung Injury / Q000175:diagnosis*; D019296:Capnography; D006801:Humans; D008168:Lung / Q000033:anatomy & histology; D010092:Oximetry; D011379:Prognosis; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D012128:Respiratory Distress Syndrome / Q000175:diagnosis* / Q000503:physiopathology