Breathable forms of pain relief for labour and birth were first used in the mid 1800's. The types used were usually chloroform or ether, mainly because they were readily available at the time. While both were effective for pain relief in labour, it was soon realised how dangerous their use could be. Women in labour often lost consciousness under their potent influence, becoming fully anaesthetised and at times stopping breathing, with devastating consequences. It was for this reason that their use was restricted to doctors with experience in anaesthesia attending births, rather than midwives (even then, this did not prevent the odd tragedy). This recommendation meant that pain relief in labour was only accessible to the affluent members of society.
Initially, well respected church leaders at the time condemned the use of pain relief for labour as being against the teachings of the church. This limited its acceptance by the general public. It was not until Queen Victoria was given chloroform in 1853 for the birth of her 7th child (Prince Leopold) that the use of breathable pain relief gained wider acceptance.
Pure Nitrous oxide was first developed by an English chemist in 1772 but it was not used as an anaesthetic for medical operations until the mid 1800's. In 1933, Dr R J Minnitt invented the 'gas and air' machine, which allowed the woman to breathe in a mixture of the nitrous oxide gas with room air, therefore achieving a level of pain relief, but not anaesthetising her to the point of losing consciousness. It was after this time that nitrous oxide became a popular form of pain relief in labour and birth, allowing midwives to safely use the drug for many years afterwards.
The machines used to administer gas in hospitals today, now mix nitrous oxide gas with pure oxygen (instead of room air). The levels of the mix can usually be adjusted to ranges from 100% pure Oxygen up to Nitrous Oxide 70% with Oxygen 30% (or 70:30).