What condition typically causes a decrease in pulmonary compliance in patients with ARDS?

The condition that typically causes a decrease in pulmonary compliance in patients with ARDS is fluid accumulation in the alveoli. In Acute Respiratory Distress Syndrome (ARDS), there is an inflammatory process that leads to increased permeability of the alveolar-capillary membrane. This results in the accumulation of fluid in the alveoli, impairing gas exchange and affecting lung compliance.

When alveoli fill with fluid, the normal air-filled alveolar structures cannot expand properly during inhalation, leading to reduced compliance. Compliance refers to the ease with which the lungs can expand; when fluid replaces air in the alveoli, it becomes increasingly difficult for the lungs to inflate, thereby decreasing compliance.

In contrast to fluid accumulation, factors like increased airway resistance would primarily influence airflow rather than lung compliance, while alveolar collapse can occur as a result but is more a consequence of the changes in lung dynamics rather than the direct cause of decreased compliance. Excessive peak airway pressure typically occurs in various clinical scenarios but does not specifically refer to the underlying pathology of ARDS related to compliance issues. Thus, fluid accumulation in the alveoli is the most direct explanation for the decrease in pulmonary compliance in this context.