In general, blood drawings will be performed from an indwelling arterial line or from a central venous line to avoid haemolysis. Blood without anti-coagulant and BALF samples will be immediately centrifuged at 3000 rpm for 10 minutes to separate the serum or the supernatants which will be immediately stored at -80°C. Data to be registered in the intensive care units The following data will be recorded either from the vital parameters monitors, from the ventilator screen or the clinical files. • Type of mechanical ventilation provided • Peak inspiratory pressure, positive end-expiratory pressure, mean airway pressure (Pāw), Expired tidal volume (pro Kg) • Total respiratory rate and spontaneous respiratory rate (if any) • Dynamic compliance over ten mechanical breaths or static compliance using end-expiratory occlusion (depending on the ventilator) § • Total respiratory system resistances over ten mechanical breaths (If patients are ventilated with high frequency oscillatory ventilation, instead of the above-mentioned parameters, Pāw, amplitude and frequency will be recorded. If a specific flow-sensor [57] is available the tidal volume delivered during oscillations will also be registered and used for further calculation [see below]).