Artificial lung support during acute respiratory failure. Alternative or complementary?

The extracorporeal support has been used to support circulation and gas exchange and was first introduced in the seventies. The equipment is composed of an external system of tubing that extracts the venous blood from the patient; the blood is driven by a pump to the artificial lung which oxygenates it and removes carbon dioxide. The blood is then circulated back to the patient. In 1973 the first randomized trial comparing the outcome of patients treated with extra-corporeal support to patients conventionally treated was performed and did not show any survival benefit (mortality equal to about 90%) and most centers, according to this result, abandoned the use of extracorporeal support in the treatment of ARDS patients. The further work of Kolobow and Gattinoni led to the introduction, in the eighties, of the extracorporeal CO2 removal, aiming at the lung rest. Different randomized studies did not show any survival benefit with extracorporeal CO2 removal support, however, the technology available at that time was likely inadequate while, nowadays, it has been greatly improved. It is important to highlight that extracorporeal supports may greatly reduce the need of mechanical ventilation which is associated to the problem of VILI. The recent H1N1 flu epidemics led to an epidemics of respiratory failure with patients considered not safely ventilable even with low tidal volume (6-8 ml/Kg) and safe plateau pressures (below 30-35 cmH2O) leading to renewed interest for extracorporeal support and to the publication of a great number of papers on the topic. Nowadays we believe that extracorporeal techniques, applied in experienced institutions, may become a feasible and promising alternative to mechanical ventilation to fully prevent VILI.