What is the primary cause of hypoxemia experienced in ARDS?

In Acute Respiratory Distress Syndrome (ARDS), the primary cause of hypoxemia is indeed fluid accumulation in the alveoli and interstitial spaces of the lungs. This condition is characterized by increased permeability of the pulmonary capillaries, leading to the accumulation of protein-rich fluid in the alveolar spaces. This fluid disrupts the normal gas exchange process, resulting in impaired oxygenation of the blood.

The presence of this fluid hinders the ability of oxygen to diffuse into the bloodstream while simultaneously preventing proper removal of carbon dioxide, leading to severe hypoxemia. The compromised ventilation-perfusion (V/Q) matching due to this fluid accumulation further exacerbates the lack of oxygen in the arterial blood.

In contrast, while airway obstruction, inadequate ventilation, and pulmonary embolism can all contribute to respiratory distress and hypoxemia in different contexts, they are not the primary mechanisms at play in ARDS. Airway obstruction may affect airway patency but does not describe the classic pathophysiological feature of ARDS. Inadequate ventilation relates to issues with how air is moved in and out of the lungs but does not directly address the accumulation of fluid in the alveoli. Finally, pulmonary embolism leads to hypoxemia through a different mechanism, primarily