Critical care

Question 1

ARDS pathogenesis

Answer 1

1. Exudative phase: injury to the lung tissue (epithelium) release of IL-6, IL-1, IL-8, AND TNF alpha, causes neutrophil recruitment and increases the permeability of the epithelium causing damage to pneumocyte I. Diffuse alveolar damage on pathology.
   - Damage to pneumocytes causes damage to the ion transport channels which in turn causes accumulation of protein rich fluid within the alveoli- this is the cause of stiff non-compliant lungs with shunt physiology
   - 7-10days
2. Proliferative phase: resolution of the non-cardiogenic pulmonary edema. Recruitment of fibroblast growth factor, pneumocyte II, and deposition of collagen causes thickening of the hyaline membrane.
   - 10-14days
3. Fibrotic stage: abnormal lung architecture, cysts
   - 14 days plus

*** ARDS may result in resolution to normal lung or fibrosis which does tend to be reversible over time.