Criteria for Clinical Diagnosis (4)

1. Time: within 1 week of the clinical insult (e.g. Post-op Complications)

2. Oxygenation: PaO2/FiO2 ≤ 300 ON ≥ 5 cm PEEP/CPAP

   • PaO2 is from ABG , normal = 100
   • FiO2 us from the Oxygen Delivery Devices
   • PEEP > 5 cm → means that Pt is appropriately ventilated, alveoli are not collapsed, but still not functional

3. Edema origin: Respiratory failure origin cannot be fully explained by cardiac failure or fluid overload (r/o cardiogenic causes)

4. Scan: CXR - Chest X ray or Thoracic CT confirming bilateral opacity

   

Relevant Physiology

Etiology

• Parenchymal Cause
  • Pneumonia → Most common
  • Aspirational Pneumonia
  • Lung contusion
  • Transfusion Complications
  • Drowning
• Extra-parenchyma Cause
  • !Sepsis → Most common
  • !Acute Pancreatitis
  • Drug
  • Trauma/ATLS (e.g. broken rib)

Pathogenesis

• Damage to type II an I pneumocyte
• Decreased surfactant secretion
• Fluid + cell debris build up in the alveoli
• Vascular endothelium damage
• Overtime → fibrosis

Consequences/Natural history

• Impaired gas exchanged (V/Q mismatch, shunt)
• PH - Pulmonary hypertension due to vasoconstriction
• Decreased lung compliance
• A cause of !Respiratory Failure