molecular oxygen;nitrous oxide

DescriptionEntonox is a 50:50 mixture of oxygen and nitrous oxide. It is produced by bubbling oxygen through liquid nitrous oxide. The two gases dissolve into each other, creating a gas mixture that does not behave in a way that could be predicted from their individual properties – the Poynting effect. Entonox is presented as a gas in French-blue cylinders with white and blue checked shoulders at a pressure of 137 bar when full. Below temperatures of –7°C (pseudocritical temperature), Entonox can separate into its constituent parts because of liquefaction of nitrous oxide. This can potentially result in the delivery of a hypoxic mixture as the cylinder empties.

Uses1. Inhalational anaesthetic agent (in conjunction with a volatile agent).2. Inhalational analgesic agent.a. During labour.b. For breakthrough pain when regional anaesthesia is used (e.g. tourniquet pain and caesarean section).c. During painful short procedures, such as change of burns dressings, manipulations of fractures/dislocations and cleaning of wounds in paediatric patients.