Episode 195: ARDS

Show Notes

Definition of ARDS:
- Non-cardiogenic pulmonary edema characterized by acute respiratory failure.
- Berlin criteria for diagnosis include acute onset within 7 days, bilateral pulmonary infiltrates on imaging, not fully explained by cardiac failure or fluid overload, and impaired oxygenation with PaO2/FiO2 ratio <300 mmHg, even with positive end-expiratory pressure (PEEP) >5 cm H2O.
Severity based on oxygenation (Berlin criteria):
- Mild: PaO2/FiO2 200-300 mmHg
- Moderate: PaO2/FiO2 100-200 mmHg
- Severe: PaO2/FiO2 <100 mmHg
Epidemiology:
- Occurs in up to 23% of mechanically ventilated patients.
- Mortality rate of 30-40%, primarily due to multiorgan failure.
Differentiation from Cardiogenic Pulmonary Edema:
- Chest CT shows diffuse edema and pleural effusion in cardiogenic edema; patchy edema, dense consolidation in ARDS.
- Ultrasound may show diffuse B lines in cardiogenic edema; patchy B lines and normal A lines in ARDS.
Pathophysiology:
- Exudative phase: Immune-mediated alveolar damage, pulmonary edema, cytokine release.
- Proliferative phase: Reabsorption of edema fluid.
- Fibrotic phase: Potential for prolonged ventilation.
Etiology:
- Direct lung injury (pneumonia, toxins, aspiration, trauma, drowning) and indirect causes (sepsis, pancreatitis, transfusion reactions, certain drugs).
Diagnostics:
- Comprehensive workup including imaging (chest X-ray, CT),