What pulmonary function changes are expected in ARDS patients?

In patients with Acute Respiratory Distress Syndrome (ARDS), a hallmark of the disease is the decrease in lung compliance due to the accumulation of fluid in the alveoli, which leads to impaired gas exchange and atelectasis (collapse of lung tissue). As a consequence of these physiological changes, one can observe a significant reduction in Functional Residual Capacity (FRC).

FRC is the volume of air remaining in the lungs after a normal exhalation, and its decrease in ARDS indicates that the lungs are less capable of maintaining adequate lung volume, which contributes to the characteristic hypoxemia seen in these patients. The other options, while they may reflect other aspects of lung function, do not accurately represent the expected changes in ARDS. For instance, an increase in vital capacity or residual volume would not typically occur in ARDS due to the restrictive nature of the lung disease, and normal lung volumes would contradict the severe impairment seen in these patients.

Thus, the identification of decreased FRC is critical in understanding the impairment of lung function associated with ARDS, reinforcing the challenges faced in managing ventilation and oxygenation in affected patients.