Ventilator-induced lung injury and sepsis: two sides of the same coin?

Unequivocal evidence from both experimental and clinical research has shown that mechanical ventilation can damage the lungs and initiate an inflammatory response, possibly contributing to extrapulmonary organ dysfunction. This type of injury, referred to as ventilator-induced lung injury (VILI), resembles the syndromes of acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS). VILI can trigger a complex array of inflammatory mediators, resulting in a local and systemic inflammatory response. Substances produced in the lungs can be translocated into the systemic circulation as a result of injury to the pulmonary epithelium and to the capillary endothelium. This type of injury forms the basis for the use of low tidal volumes (5-7 mL/kg of predicted body weight) during mechanical ventilation of patients with ALI/ARDS. The recognition of VILI has prompted a number of investigators to suggest that ALI/ARDS may be, in part, a product of our efforts to mechanically ventilate patients rather than the progression of the underlying disease. On the other hand, current scientific evidence supports a link between VILI and the development of extrapulmonary organ dysfunction, similar to how most severe cases of sepsis are clinically manifested. In addition, functional genomics approaches using a gene array methodology to measure lung gene expression have identified differential patterns of gene expression in animal models of VILI, similar to those gene pathways activated during experimental and clinical sepsis. In this line of thought, we hypothesize that injurious mechanical ventilation could be responsible for the perpetuation and worsening of sepsis in some patients and for the development of a sepsis-like syndrome in others.