109 patients who suffered from an episode of acute respiratory failure, necessitated mechanical ventilation (MV) in a general Intensive Care Unit (ICU) and admitted to our Respiratory Intermediate Intensive Unit (RIIU), were retrospectively evaluated for outcome and weaning success. The patients, 69 +/- 9 years old, presented the following diseases: COLD (70%), cardiovascular (15%) and neuromuscular (15%). A relapse of underlying disease (62%), pneumonia (20%), thoraco-muscular pump failure (15%) and pulmonary embolism (3%) were the relapsing causes needing the ICU admission. Patients remained intubated for 12 +/- 6 days and ventilated for 25 +/- 10 days. They were transferred to RIIU on pressure support ventilation (70%); the causes of prolonged and/or difficult weaning were as following: lung failure (48%), pump failure (12%), cardiac and haemodynamic instability (28%) others (12%). Apache II score was 18 +/- 5. Maximal inspiratory pressure (31 +/- 7 cmH2O) and respiratory rate/tidal volume (83 +/- 34) were measured within 48 hours after RIIU admission. 82 subjects (75%) were weaned after 6 +/- 4 days of MV using in 87% of patients pressure support technique with spontaneous breathing cycles with oxygen supplementation. 8 patients on 109 (7%) died; 20 patients on 109 (18%) were discharged after 40 +/- 9 days of stay in RIIU necessitating home MV more than 18 hours/day by means of a tracheostomy. All patients stay in RIIU for 17 +/- 7 days with a mean cost per die of 750 thousands lire. Our data suggest that a RIIU institution for prolonged weaning in chronic diseases may be a useful solution to decrease superfluous stays in ICU decreasing costs without ba worsening in quality of care.