Parallel two group double blind randomized controlled clinical trial. Individual randomization, performed on day 4 of invasive mechanical ventilation, will be stratified on centre in order to account for variations in VAP prevention bundle implementation and use of systemic antibiotics the day of randomization. Patients will be treated three consecutive days with inhaled amikacin or placebo. Patients will be followed up daily in the intensive care unit for the occurrence of VAP according to international guidelines until day 28.