Entonox is a pain relieving (analgesic) gas used by first responders and ambulance staff across the world. Entonox is a mix of Oxygen (50%) and Nitrous Oxide (50%). Nitrous Oxide is also known more commonly as laughing gas. 

Some advanced first aiders may be trained in the use of Entonox. It’s main advantages are rapid onset (within seconds) and there is no need to establish intravenous access as Entonox is inhaled. 

However there are certain conditions which can be worsened by the use of Entonox. A first aider should always consider these contraindications before making a decision to use Entonox. 

The contraindications of Entonox

Entonox should not be used in the following situations:

• Suspected pneumothorax (air in the chest cavity)
• Following a recent dive
• Severe abdominal distension
• Head injuries
• Severe facial injuries
• Any condition affected the ability of the patient to inhale the gas independently (eg: intoxication or sedation) 

Entonox can cause any gas trapped within the body to expand. Therefore it has the potential to worsen a pneumothorax or intestinal obstruction.

If you are trained in the use of Entonox it is important you follow your local protocols and training.