Foundation Concept

Core Question

Is enough oxygenated blood reaching the tissues — not just “what is the sat?”

Core Concept

Oxygen delivery depends on more than arterial oxygen saturation.

It depends on:

1. Blood flow / cardiac output

   How much blood reaches the tissues.

2. Oxygen content

   How much oxygen the blood carries. This is influenced by hemoglobin and arterial oxygen saturation.

3. Flow distribution

   Where the blood is actually going.

This becomes especially important in congenital heart disease because oxygenation and perfusion do not always move together.

A patient may have an acceptable saturation while systemic flow, regional perfusion, or oxygen delivery is already strained.

The key concept:

Saturation tells you oxygenation.It does not prove oxygen delivery.

Why Saturation Alone Is Incomplete

Arterial saturation tells you how oxygenated the blood is.

It does not tell you whether enough blood is reaching the tissues.

A patient may have:

• normal or acceptable saturation with poor flow

  → poor oxygen delivery