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

1. Load the trucks → increase saturation (SaO₂)

• FiO₂ / FdO₂

• Oxygenation

2. Add more trucks → increase hemoglobin (Hgb)

• Transfusion

• Oxygen-carrying capacity

3. Move them faster → increase flow (Q)

• ECMO flow (see note below)

• Cardiac output

Quick Bedside Check

If oxygen delivery is low, ask:

• Is saturation adequate?

• Is hemoglobin adequate?

• Is the flow adequate?

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:

• Minimal gain in delivery

• 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.

Learn More

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Educational content only. Follow your institutional protocols and clinical judgment.