OBJECTIVES: Mechanical ventilation for acute respiratory failure is likely to be a reliable indicator of critical care resource requirements on a population level. Our aim is to analyze the costs and discharge status for patients with respiratory failure needing mechanical ventilation (DRG code 475) in Spain and to examine the impact of age in terms of hospital outcome. METHODS: . From the 2004 National Hospital Discharge Database all records aged >16 years with a final DRG 475 were retrieved. This DRG, defined as “respiratory system diagnosis with mechanical ventilation”, includes three procedure codes and is applied to patients undergoing mechanical ventilation for a variable period of time. Demographic characteristics, clinical outcomes and hospital-resources utilization were examined. An exploratory logistic regression analysis was performed to identify factors associated with in-hospital mortality. To depict the amount of resources spent to procure a given level of desired outcome (hospital survival) we determined the cost per survivor based in the average national charges for DRG 475. RESULTS: 4267 cases were eligible for analysis. Mean age was 64yr, 71% were men and 85% medical patients. According to Charlson index, 45% of cases had no associated comorbidity. Overall 36% of cases required prolonged mechanical ventilation. In-hospital mortality was 39%. Median LOS was 14 days. Total hospital costs were ª 42,581,929. Multivariate logistic regression showed that age significantly correlated with in-hospital mortality after adjusting for comorbidities, principal cause of hospital admission and duration of mechanical ventilation. An inverse relationship between survival rate and age was observed and this resulted in an age-related increased cost per survivor. CONCLUSIONS: . Age has a significant impact on outcomes in patients under DRG 475.  These analyses will help inform health care decision-making and resource planning in the face of an ageing population. This study has been supported by the Spanish National I+D Program (grant number STPY 1456/07).