Bench-to-bedside review: chest wall elastance in acute lung injury/acute respiratory distress syndrome patients.
The importance of chest wall elastance in characterizing acute lung injury/acute respiratory distress syndrome patients and in setting mechanical ventilation is increasingly recognized. Nearly 30% of patients admitted to a general intensive care unit have an abnormal high intra-abdominal pressure (due to ascites, bowel edema, ileus), which leads to an increase in the chest wall elastance. At a given applied airway pressure, the pleural pressure increases according to (in the static condition) the equation: pleural pressure = airway pressure x (chest wall elastance/total respiratory system elastance). Consequently, for a given applied pressure, the increase in pleural pressure implies a decrease in transpulmonary pressure (airway pressure - pleural pressure), which is the distending force of the lung, implies a decrease of the strain and of ventilator-induced lung injury, implies the need to use a higher airway pressure during the recruitment maneuvers to reach a sufficient transpulmonary opening pressure, implies hemodynamic risk due to the reductions in venous return and heart size, and implies a possible increase of lung edema, partially due to the reduced edema clearance. It is always important in the most critically ill patients to assess the intra-abdominal pressure and the chest wall elastance.
Institute of Anesthesia and Critical Care, University of Milan, Policlinico - IRCCS Hospital, Milan, Italy. gattinon@policlinico.mi.it
Luciano
L
Gattinoni
Davide
D
Chiumello
Eleondra
E
Carlesso
Franco
F
Valenza
D006801:Humans; D007362:Intensive Care Units; D008170:Lung Compliance / Q000502:physiology*; D012121:Respiration, Artificial; D012128:Respiratory Distress Syndrome / Q000503:physiopathology* / Q000628:therapy; D035441:Thoracic Wall / Q000503:physiopathology*