Objective: To define the occurrence rate of acute respiratory distress syndrome (ARDS) using established criteria in a well-defined general patient population, to study the clinical course of ARDS when patients were ventilated using a lung-protective strategy, and to define the total costs of care. Design: A 3-yr (1993 through 1995) retrospective descriptive analysis of all patients with ARDS treated in Kuopio University Hospital. Setting: Intensive care unit in the university hospital. Patients: Fifty-nine patients fulfilled the definition of ARDS: Pao 2 /Fio 2 < 200 mm Hg (33.3 kPa) during mechanical ventilation and bilateral infiltrates on chest radiograph. interventions: None. Measurements and Main Results: With a patient data management system, the day-by-day data of hemodynamics, ventilation, respiratory mechanics, gas exchange, and organ failures were collected during the period that Pao 2 /Fio 2 ratio was
