The prediction of duration of mechanical ventilation (MV) is difficult. Vital capacity, forced expiratory volume in one second (FEV1) and arterial oxygen pressure, before surgery can predict the duration of MV. For emergency intubation, respiratory parameters cannot be measured before the tracheal intubation. Prognostic factors such as nutritional depletion as assessed by body mass index (BMI) and serum albumin and overall systemic inflammation as estimated by C-reactive protein (CRP) appear to be major determinants of hospitalization.