Description
Acute Lung Injury (ALI) and Acute Respiratory Distress Syndrome (ARDS) are defined as:
- Bilateral pulmonary infiltrates on chest x-ray
- Pulmonary Capillary Wedge Pressure < 18 mmHg (2.4 kPa)
- PaO2/FiO2* <300 mmHg (40 kPa) = ALI
- PaO2/FiO2 <200 mmHg (26.7 kPa)= ARDS
There are two forms of ALI. Primary ALI is caused by a direct injury to the lung (e.g., pneumonia). Secondary ALI is caused by an indirect insult (e.g., pancreatitis). There are two stages – the acute phase characterized by disruption of the alveolar-capillary interface, leakage of protein rich fluid into the interstitium and alveolar space, and extensive release of cytokines and migration of neutrophils. A later reparative phase is characterized by fibroproliferation and organization of lung tissue.
The patient has low lung volumes, atelectasis, loss of compliance, ventilation-perfusion mismatch (increased deadspace), and right to left shunt.
Clinical features are – severe dyspnea, tachypnea, and resistant hypoxemia.
Read more about this topic: Acute Lung Injury
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