A prospective, international and multicenter, non interventional single-cohort study, which will enroll consecutive adult patients who have received mechanical ventilation (invasive and noninvasive ventilation) for at least 12 hours during a 1-month period, and will follow each patient for the duration of mechanical ventilation, up to 28 days. The main objectives will be to analyze the mortality and clinical outcomes in ventilated patients and secondly, to evaluate the practices of liberation from mechanical ventilation, the failure of non invasive ventilation in the ICU, and to analyze the clinical outcomes in specific populations of critically ill patients with the need of mechanical ventilation.