Overview
Definition
An acute, diffuse, inflammatory lung injury leading to increased pulmonary vascular permeability, increased lung weight, and loss of aerated lung tissue.
Epidemiology
High mortality rate (~30-40%). Most commonly seen in the ICU.
Etiology & Risk Factors
- Sepsis (most common indirect cause)
- Pneumonia (most common direct cause)
- Aspiration of gastric contents
- Trauma / Shock / Massive transfusion
Clinical Symptoms
- Severe dyspnea occurring within 1 week of a known clinical insult
- Rapid breathing (tachypnea)
- Profound hypoxemia refractory to supplemental oxygen
Clinical Approach
Diagnosis
- Berlin Criteria: (1) Acute onset within 1 week, (2) Bilateral opacities on CXR/CT not fully explained by effusions/collapse/nodules, (3) Respiratory failure not fully explained by heart failure or fluid overload, (4) PaO2/FiO2 ratio < 300 mmHg
Management
- Treat the underlying cause (e.g., antibiotics for sepsis)
- Mechanical Ventilation: Low tidal volume ventilation (6 mL/kg predicted body weight) to prevent volutrauma
- Permissive hypercapnia
- Prone positioning (in severe ARDS, P/F ratio < 150)
- Neuromuscular blockade (paralytics) if ventilator dyssynchrony occurs
Complications
- Barotrauma (Pneumothorax)
- Ventilator-Associated Pneumonia (VAP)
- Deep Vein Thrombosis / PE
- Pulmonary fibrosis in survivors