What is the hemodynamic effect of prone positioning in ARDS?

• A. Worsened oxygenation with no hemodynamic risk
• B. Always improves hemodynamics
• C. Improved oxygenation with potential hemodynamic compromise
• D. No effect on oxygenation

Answer: (C)

Prone positioning in ARDS improves oxygenation by more evenly distributing lung ventilation and promoting recruitment of the dorsal lung fields, which enhances ventilation–perfusion matching and reduces shunt. This often leads to better PaO2/FiO2 and overall oxygenation. At the same time, changing to a prone posture can affect hemodynamics because it may increase intrathoracic and abdominal pressures, potentially reducing venous return and preload. In patients who are preload-responsive or have high PEEP, this can cause a temporary decrease in cardiac output or blood pressure. So you often see improved oxygenation with a real, but not universal, risk of hemodynamic compromise that clinicians monitor closely during positioning and adjust fluids or vasopressors as needed.