Veno-venous ECLS treatment (ECMO) was applied in case of severe ARDS not responsive to conventional treatments, but potentially reversible. Conditions of severe hypoxia or hypercapnia, where the limits of a pro-tective ventilation strategy could not be maintained (tidal volume less than 6 mL/Kg of predicted body weight and plateau pressure less than 30 cmH 2 O), were the indications for starting extracorporeal circulation [11] . The Careggi Teaching Hospital had started a collaboration with the ICUs of 12 district hospitals in Tuscany in a pilot project for centralization of acute lung injury/ARDS patients who require (or may require) ECLS treatment. In 2008 and spring 2009, preliminary meetings were organized to inform the peripheral hospitals' ICU staff and Administrations about the availability of the new ECLS program. During the H1N1 influenza A pandemic, the knowledge of ECMO treatment rapidly spread among the medical community and the Regional Ministry of Health issued indications to transfer all patients affected by severe respiratory failure related to influenza to Careggi Hospital. In Appendix 1 is reported the set of parameters that were adopted to quickly detect patients suitable for extracorporeal treatment in the peripheral hospitals. Patients deemed suitable for ECMO treatment were evaluated on site by the ECMO team. Depending on clinical condition, the transfer was performed on conventional ventilation or, alternatively, ECLS treatment was initiated in the peripheral hospital and maintained during transportation [12] . We preferentially adopted a high flow technique (5-6 litres per minute of blood flow), to maximize the opportunity of providing protective ventilation, aiming to achieve a plateau pressure below 28 cm H 2 O and PEEP 2 cmH 2 O above the lower inflection point of the quasistatic pressure volume curve, regardless the delivered tidal volume (in any case less than 6 ml/kg). Controlled respiratory frequency was reduced to 4-10/min to maintain normocapnia. Inspired oxygen fraction was reduced to 0.5 or lower, whenever possible. A recruitment manoeuvre was performed at least once a day, and ventilation with an intermittent high pressure breath ("sigh") was adopted to improve lung aeration [13] . During ECMO, nitric oxide administration [14] , vasoactive support, and prone positioning were maintained or initiated according to clinical conditions.