The investigators propose to perform a one-year prospective audit of all Acute lung injury (ALI)and cute respiratory distress syndrome (ARDS) pediatric patients managed in several ICUs in Spain. The investigators intend to collect data from all children (from 1 month to 18 years of age) admitted with or developing ALI/ARDS with the aim to understand the epidemiology and natural history of acute lung injury in the pediatric setting. These ICUs are scattered through the Spain and are representative of the demographic differences across the country.

Acute lung injury (ALI) is a clinical syndrome of rapid onset of non-cardiogenic pulmonary edema manifested clinically by hypoxemia (PaO2/FiO2≤300 mmHg) and bilateral pulmonary infiltrates. When the hypoxemia is severe (PaO2/FiO2≤200 mmHg) it is termed the acute respiratory distress syndrome (ARDS). It represents a significant public health issue. Patients with ALI or ARDS require admission into critical care units for advanced life support and utilize considerable health care resources.

An immense plethora of translational knowledge has been acquired since the first description of ARDS in 1967. At the present, estimates of the incidence of ARDS and ALI in children are unknown. In adults, the estimates of ALI/ARDS incidence have varied widely, and the true magnitude of this health problem still remains unclear. Current estimates of the incidence of adult ALI/ARDS range from 15 to 80 cases per 100.000 population, or almost 40.000 cases per year in Spain. Combined mortality rates for adult ALI/ARDS range between 30-45% but it is not clear whether this figures can be translated in the pediatric population. ALI and ARDS occur as a complication or as the primary cause of critical illness in patients, usually after severe infection or trauma.

Published epidemiological studies on ALI and ARDS in the last 20 years are difficult to compare. Some reports have used different definitions for ALI and ARDS and others have evaluated the incidence during a short period of time (from days to several weeks) and then extrapolated their data to estimates of a one-year incidence. Very few studies have collected information for an entire year, and none of them have evaluated the degree of hypoxemia under standard ventilatory settings, as it has been proposed recently by the HELP Network (Am J Respir Crit Care Med 2007; 176:795-804).

Inclusion criteria:

• All patients, age ranging from 1 month to 15 years old
• Must be able to meet the American European Consensus definition of ALI and ARDS(no indication of heart failure or a pulmonary capillary wedge pressure of greater than 18 mmHg, with pulmonary infiltrates in all four quadrants and a PaO2/FIO2 of > 200 to <300 mmHg (ALI) or ? 200 mmHg (ARDS).

Exclusion criteria:

• Younger than 1 month or older than 15 years old
• Cardiac disease

All patients, age ranging from 1 month to 18 years old, meeting the American European Consensus (AECC) definition of ALI and ARDS will be included regardless of etiology of respiratory failure.