Acute Lung Injury (ALI) refers to the spectrum of acute diffuse pulmonary injury resulting in respiratory compromise, ranging from mild to severe. Acute Respiratory Distress Syndrome (ARDS) refers to the most severe end of the spectrum. The inciting injury may occur either directly to the airways or indirectly via the bloodstream.
Terminology
• Use of term "acute" is preferable to that of "adult" for expansion of "ARDS".
• All patients with ARDS have acute lung injury but not all patients with acute lung injury have ARDS.
Criteria
Acute Lung Injury
Acute Respiratory Distress Syndrome
onset
acute
acute
oxygenation
PaO2/FIO2 < 300 mm Hg, regardless of PEEP level
PaO2/FIO2 < 200 mm Hg regardless of PEEP level
frontal chest radiograph
diffuse, bilateral infiltrates, compatible with pulmonary edema
diffuse, bilateral infiltrates, compatible with pulmonary edema
pulmonary artery wedge pressure (if available)
<= 18 mm Hg
<= 18 mm Hg
clinical findings (if pulmonary artery wedge pressure not available)
no clinical evidence of left atrial hypertension or congestive heart failure
no clinical evidence of left atrial hypertension or congestive heart failure
where:
• At high altitudes the level of the PaO2/FIO2 ratio may have to be adjusted, and a PaO2/PAO2 ratio of < 0.20 has been used.
• Originally decreased lung compliance was included in the defining criteria for ARDS.
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