POTENTIAL, PROTOCOL-RELATED RISKS AND THEIR PREVENTION Potential risks: Hypoxemia, Hypercapnia, Hemorrhage, Arrhythmias, Barotrauma. Preventive measures: Pre-oxygenation and titration of sedation. ContinUous monitoring of cardio-respiratory parameters during bronchoscopy. Bronchoscopy by an experienced endoscopist, in the presence of an experienced operator of the conventional ventilator. Use of maximal internal diameter tracheal tube, in conjunction with a minimal outer diameter bronchoscope. Potential benefits: BAL culture for reliable identification of pathogens, with consequent use of a targeted antibiotic treatment and avoidance of unnecessarily broad antibiotic regimens. The second BAL sample will enable the confirmation of the effectiveness of the antibiotic treatment through the documentation of the reduction in the concentrations of the colony forming units of the pathogens.