Oxygen Delivery (DO₂) — Bedside Thinking
The Truck Analogy
When a patient isn’t improving, it’s easy to chase the PaO₂.
But oxygen delivery depends on three things.
Think of hemoglobin like a truck carrying oxygen to tissues.
The Three Levers
- Load the trucks → increase saturation (SaO₂)
Load up the trucks = Increase FiO2
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FiO₂ / FdO₂
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Oxygenation
- Add more trucks → increase hemoglobin (Hgb)
More trucks on the road = Transfuse, increase Hb
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Transfusion
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Oxygen-carrying capacity
- Move them faster → increase flow (Q)
Trucks driving faster = Increase ECMO Flow
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ECMO flow (see note below)
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Cardiac output
Quick Bedside Check
If oxygen delivery is low, ask:
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Is saturation adequate?
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Is hemoglobin adequate?
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Is the flow adequate?
Fix the weak link
Look at the problem with an open mind and fix it.
Common Mistake
Low PaO₂ → increase FiO₂
Helps—but only to a point.
Beyond that:
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Minimal gain in delivery
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Rising PaO₂ may be harmful
Think: Hb + Flow + Saturation—not PaO₂ alone.
Important Note: VV vs VA ECMO Response
Takeaway
Saturation + Hemoglobin + Flow = Oxygen Delivery
Don’t chase PaO₂ in isolation.
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Educational content only. Follow your institutional protocols and clinical judgment.