What is the primary characteristic of ARDS?

The primary characteristic of Acute Respiratory Distress Syndrome (ARDS) is increased alveolar-capillary permeability. This condition leads to a significant increase in the permeability of the alveolar-capillary membrane, which results in the accumulation of fluid in the alveoli. This fluid exudation impairs gas exchange, leading to severe hypoxemia and respiratory failure.

Understanding this mechanism is crucial in the context of ARDS, as it underlies many of the clinical manifestations seen in affected patients. Increased permeability allows protein-rich fluid to leak into the alveolar space, which disrupts normal lung function and can lead to pulmonary edema. Recognizing increased permeability as a hallmark of ARDS helps healthcare professionals identify and manage the condition effectively.

The other options, while potentially related to complications or consequences of ARDS, do not capture its central pathophysiological feature. Severe lung inflammation with decreased blood flow may occur, but inflammation alone does not define ARDS. Progressive failure of multiple organ systems can result from severe hypoxemic conditions, but it is not a direct characteristic of ARDS itself. Fluid accumulation in the abdomen refers more to conditions like ascites, which are unrelated to the defining features of ARDS.