[Permissive and non-permissive hypercapnia: mechanisms of action and consequences of high carbon dioxide levels].

Acute lung injury is a disease with high incidence of mortality and its treatment is still controversial. Increasing the levels of CO2 beyond the physiological range has been proposed as a potential protective strategy for patients on mechanical ventilation, as it could moderate the inflammatory response. In this article we review the published evidence on the role of CO2 during acute lung injury. We conclude that although there are reports suggesting benefits from hypercapnia, more recent evidence suggests that hypercapnia could be deleterious, contributing to worsening of the lung injury.