A distinct type of hypoxemic respiratory failure characterized by acute abnormality of both lungs was first recognized during the 1960s. Military clinicians working in surgical hospitals in Vietnam called it shock lung, while civilian clinicians referred to it as adult respiratory distress syndrome . Subsequent recognition that individuals of any age could be afflicted led to the current term, acute respiratory distress syndrome (ARDS).
The Berlin Definition of ARDS (published in 2012) has replaced the American-European Consensus Conference’s definition of ARDS (published in 1994) [2,3]. However, it should be recognized that most evidence is based upon prior definitions. The current diagnostic criteria for ARDS are provided separately. (See "Acute respiratory distress syndrome: Clinical features and diagnosis", section on 'Diagnostic criteria'.)
The epidemiology, pathophysiology, pathologic stages, and etiologies of ARDS will be reviewed here. Other issues related to ARDS are discussed separately. (See "Acute respiratory distress syndrome: Clinical features and diagnosis" and "Acute respiratory distress syndrome: Prognosis and outcomes" and "Mechanical ventilation in acute respiratory distress syndrome" and "Supportive care and oxygenation in acute respiratory distress syndrome" and "Novel therapies for the acute respiratory distress syndrome".)
The incidence of ARDS was determined in a multicenter, population-based, prospective cohort study in the United States . The study followed 1113 patients with ARDS for 15 months beginning in 1999 or 2000:
- The age-adjusted incidence was 86 per 100,000 person-years for individuals with an arterial oxygen tension to fraction of inspired oxygen ratio (PaO2/FiO2) ≤300 mmHg and 64 per 100,000 person-years for individuals with a PaO2/FiO2 ≤200 mmHg.
- The incidence increased with patient age from 16 per 100,000 person-years among individuals 15 to 19 years of age to 306 per 100,000 person-years among individuals 75 to 84 years of age.
- Extrapolation of the data suggested that there are approximately 190,000 cases of ARDS in the United States each year .