What Determines Oxygen Delivery?

The pathophysiology underlying shock varies enormously from cause to cause.

Take a moment to think about the key factors that determine global oxygen delivery i.e. the amount of oxygen leaving the left ventricle every minute [7,9].

Global oxygen delivery is determined by cardiac output (CO) and arterial oxygen content (CaO₂).

CO is heart rate (HR) x stroke volume (SV).

The vast majority of oxygen carried in the blood is bound to haemoglobin. Only a tiny proportion is in solution (measured by PaO₂). So the main determinants of arterial oxygen content are oxygen saturation and haemoglobin concentration.

For practical purposes global oxygen delivery can be calculated as:

(HR x SV) x [Hb]g/dl x 10 x 1.34 x sO₂ ml/l

Where:

• The 10 is to convert g/dl of Hb to g/l
• The 1.34 represents the amount of oxygen (in ml) carried by one gram of 100% saturated haemoglobin