Blood gases

A blood gas test assesses whether the body is short of oxygen and is part of the investigation into symptoms of breathlessness, cough, and fever.

A small sample of blood is taken from an artery either at the wrist or in the groin where a pulse can be felt. This procedure can cause some pain and discomfort, but the use of a local anaesthetic should reduce this.

The result reflects how the lungs are functioning and gives an indication of the severity of underlying problems. This information helps in assessing problem severity and deciding the course of treatment.

Taking blood gases is not always necessary. In many situations (e.g. in initial assessment and routine monitoring) it is being replaced by use of a pulse oximeter, that involves attaching a probe to a finger and measuring the level of oxygen saturation in the blood. The advantage of a pulse oximeter is that it is simple and non-invasive. Unfortunately, it does not provide as much information as does an arterial blood gas analysis.