Final answer:
In the exudative phase of ARDS, the pathophysiological changes begin with damage to the alveolar-capillary barrier, leading to fluid leakage, formation of hyaline membranes, inflammation, neutrophil infiltration, and disrupted surfactant production, culminating in compromised gas exchange and hypoxemia.
Step-by-step explanation:
The exudative phase of acute respiratory distress syndrome (ARDS) involves a sequence of pathophysiologic changes which occur as follows:
- Initial damage to the alveolar-capillary barrier occurs, leading to increased permeability.
- This increased permeability allows leakage of protein-rich fluid into the alveoli, which disrupts the balance of oncotic and hydrostatic pressures.
- The accumulation of fluid and proteins in the alveolar spaces results in the formation of hyaline membranes, which further impairs gas exchange.
- In response, the inflammatory process is initiated, leading to the infiltration of neutrophils and other inflammatory cells into the interstitial and alveolar spaces.
- These cells release inflammatory mediators, which can cause further damage to the alveolar-capillary membrane and exacerbate the leak of fluid.
- Finally, surfactant production is disrupted, aggravating atelectasis (collapse of alveoli) and decreasing lung compliance.
These events all contribute to compromised gas exchange, manifesting in hypoxemia and respiratory distress.