What does "prone positioning" do for patients with ARDS?

Prone positioning significantly benefits patients with Acute Respiratory Distress Syndrome (ARDS) mainly by improving oxygenation. When patients are placed in a prone position, the distribution of lung perfusion and ventilation changes favorably. This positioning helps to recruit collapsed areas of the lungs, improves the ventilation-perfusion ratio, and allows for more effective ventilation, which can enhance overall oxygen exchange.

In ARDS, the lungs often have regions that are poorly ventilated due to fluid accumulation or atelectasis. Prone positioning can help open these regions, leading to better oxygen delivery to the blood and reducing the need for higher levels of supplemental oxygen. The posture also aids in preventing further deterioration of lung function that can result from mechanical ventilation when patients are placed on their backs.

While other factors, such as airway clearance and reduction of pressure sores, may be important in comprehensive care, the primary and most researched effect of prone positioning in ARDS is the improvement of oxygenation, making option B the most appropriate choice.