The acute respiratory distress syndrome (ARDS) is characterized by the following criteria as defined by the European-American Consesus Conference (EACC) (1):

• acute onset of lung disease
  
• bilateral pulmonary infiltration
  
• no clinical signs of left ventricular failure /  the PCWP is below 18 mmHg
  
• occurence of hypoxemia (PaO₂/F_IO₂ < 200 mmHg is an ARDS; PaO₂/F_IO₂ < 300 mmHg is an acute lung injury, ALI)                

The incidence of the syndrom varies in newer studies between 1.5 cases für the severe ARDS with a P/F ratio < 110 and 88.6 cases per 100000 inhabitants and year for the acute lung injury (ALI) (2). German data exist for the region of Berlin from the year 1995 (3). For Europe the ALIVE trial which was performed in 78 ICUs in 10 countries has suggested a mortality for ARDS of 57.9% and for ALI of 49.4%. Mean duration of ICU stay was for ARDS patients 16.3 days and for ALI 16.5 days respectively. In contrast to ALI the ARDS is a rare disease and the long ICU stay and high mortality require a large medical effort for a successful therapy.

The relevance of evidence based medicine regarding the process- and outcome-quality in ARDS is difficult to judge due to the multimodal therapy (ventilation strategies, hemodynamic support, extracorporeal lung support). In some of these modules EBM-guidelines might be implemented, in others not. Therefore process- and outcome-quality can differ in multicenter trials where one these treatment modalities is studied.

1. Bernard G, Artigas A, Brigham K, Carlet J, Falke K, Hudson L, Lamy M, Legall J, Morris A, Spragg R. The American-European Consensus Conference on ARDS. Definitions, mechanisms, relevant outcomes, and clinical trial coordination. Am J Respir Crit Care Med 1994; 149:818-24.
2. Rubenfeld GD. Epidemiology of acute lung injury. Crit Care Med 2003; 31:S276-S284.
3. Lewandowski K, Metz J, Deutschmann C, Preiss H, Kuhlen R, Artigas A, Falke KJ. Incidence, severity, and mortality of acute respiratory failure in Berlin, Germany. Am J Respir Crit Care Med 1995; 151:1121-5.
4. Brun-Buisson C, Minelli C, Bertolini G, Brazzi L, Pimentel J, Lewandowski K, Bion J, Romand JA, Villar J, Thorsteinsson A, Damas P, Armaganidis A, Lemaire F; ALIVE Study Group. Epidemiology and outcome of acute lung injury in European intensive care units. Intensive Care Med 2004; 30:4-6.
5. The acute respiratory distress sysndrom network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. NEJM 2000; 342(18):1301-8