How does CPR work if you exhale Carbon Dioxide?

Have you ever wondered how rescue breaths in Cardiopulmonary Resuscitation (CPR) work? Surely, we breath out Carbon Dioxide so how does breathing into a patient help?

Everyone learns at school that we breath in Oxygen (essential for life!) and breath out Carbon Dioxide (a waste product). It seems a bit strange then that we want to breath out into a patient?

To answer this question we need to look at some numbers:

Air in the atmosphere that we breath in contains around 21% Oxygen. If you read different sources they will all give you slightly different figures however the figure is around 21%.

Our body only uses around 5% of the Oxygen that we breath in. As a result, our exhaled breath contains approximately 16% Oxygen.

This 16% is more than enough to supply through rescue breathing.

It is worth noting that some countries do not teach rescue breathing to lay members of the public, instead hands only CPR is taught to members of the public in an attempt to simplify actions in an emergency.