Acute Respiratory Distress Syndrome (ARDS) is a syndrome of inflammation and increased pulmonary alveolar permeability associated with a constellation of clinical, radiologic and physiologic abnormalities. The functional lung injury is identified histologically as diffuse damage to the alveolar-capillary unit. Disruption of the endothelial barrier in the pulmonary alveolocapillary membrane leads to non-cardiogenic pulmonary edema through increased vascular permeability. Gas exchange and mechanical properties of the lung are impaired as fluid fills the alveoli. When functional lung injury is severe, the patient clinically manifests ARDS
In 1994, the American-European Consensus Conference established the defining criteria:
- New, bilateral, diffuse, patchy or homogeneous pulmonary infiltrates on radiograph
- Occurring in the appropriate clinical setting with one or more recognized risk factors
- Without clinical evidence of heart failure, fluid overload or chronic lung disease
(pulmonary arterial occlusion \"wedge\" pressure <18 mmHg) - Impaired oxygenation defined as the ratio of the partial pressure of arterial oxygen (PaO2) to the fraction of inspired oxygen (FiO2) <200 regardless of the level of PEEP
IMPORTANT NEGATIVE X-RAY FINDINGS
1.NO CARDIOMEGALY . 2.NO PLEURAL EFFUSION 3. NO KERLEY B LINES
IMPORTANT POSITIVE X-RAY FINDINGS
1.PERIHILAR DISTRIBUTION OF PATCHY INFILTRATES 2. AIR BRONCHOGRAM.
CT scan reveals ground-glass opacities and heterogeneous consolidation distributed peripherally and mainly in the dependent portions of the lung, but it also can include patchy infiltrates with lung areas of normal appearance.