Intubation & Ventilation Scenario 5

Failure to Oxygenate:

Solution

This is, in many ways the opposite to case 4. The patient is hypotensive, hypoxemic and hypocarbic after pelvic surgery. The most likely diagnosis is a massive pulmonary embolism from the pelvic veins. The problem is failure of oxygenation due to a massive amount of wasted ventilation (dead space ventilation), due to obstruction of blood flow. The fraction of dead space is calculated from the equation PaCO2 - PetCO2 / PaCO2 (PetCO2 is the end tidal CO2). It is usually 30% or less. If the dead space fraction is very high then there is wasted ventilation; the usual cause of this is increased alveolar dead space due to alveolar collapse/consolidation. In this case it is due to cardiovascular obstruction.