History of Entenox/Nitrous Oxide

Childbirth is not easy. Many women suffer during childbirth. Childbirth is meant to be hard, long, and painful – but women are strong and our bodies are made to handle a lot during this difficult time. Thousands of women have been giving birth in spite of the labour pain. Unfortunately many women do not cope well with labour pain. For some, the pain can be overwhelming.

Several studies had been done on childbirth. Hundreds of women in different countries were interviewed, and all participants said birth contractions were bittersweet, with paradoxial, feelings of love and the challenges of pain culimating in the birth of a child. The description of the pain included burning stinging, cramping, stabbing, hot, heavy, throbbing, tiring, exhausting and intense. The participants of the study also said that giving birth was seen as a difficult, yet empowering experience.

It is for this reason that scientist have been looking for ways to relieve the pain associated with childbirth. The history of childbirth facinates me and I found it hard to focus on just one detail. I set out to explore the reason behind the development of anesthesia. I came across the birth of Queen Victoria and the birth of her last two babies. I was curious to how and when she changed the mind of the clergy for good.

Anaesthetics came into use in the mid-1800’s as new chemical compounds were discovered and became available for experiments. Many of the commonly used anaesthetics are simple chemical compounds, and cover a surprising range of substances. The literature shows that the first anaesthetics were discovered when experimenters tried inhaling gases, or the vapours of volatile liquids. It all started with the brilliant mind of Sir James Young Simposon, who was a Scottish obstetrician in the 1800. Simpson had begun using ether to relieve the pain of childbirth, but he was dissatisfied with some of ether’s drawbacks, such as its disagreeable smell, the large quantities required, and the lung irritation it caused. Ether was also explosive so and many did not like to use.

It was during this time when a Liverpool chemist, David Waldie, suggested that Simpson try chloroform. On the evening of November 4, 1847, Simpson and two doctor friends inhaled some chloroform and, after feeling very happy and talkative, promptly passed out. They were so impressed with chloroform’s potency and rapid effects, that Dr Simpson immediately began using it in his obstetrical practice. Because of this experience the first baby born to a mother who received chloroform for pain was named Anaesthesia.

Unfortunately, the church objected to the use of chloroform, insisting the pain of childbirth was ordained by God, referring to the Bible where God punish Eve somewhere in Genesis. “To the woman He said, ” I will greatly increase your pains in chidbearing; with pain you will give birth to children.” The argument continued until 1853, when Queen Victoria chose to be chloroformed for the birth of her 8th son Prince Leopold. Dr. John Snow (1813-1858), who administered the chloroform to the queen, became the foremost authority on anesthesia and is recognized today as the world’s first professional anesthetist, a pioneer of a new medical specialty.

The queen enjoyed the birth of her son and used it again for her last pregnancy. This event quieted the clergy and made chloroform the most fashionable anesthetic—especially in England —for the next 50 years. Jason Priestly, an English chemist produced nitrious oxide in 1776. He could not use this because of the church but after Queen Victoria used chloroform successfully, it was time to investigate the matter further. However the first medical use seems to have been in the U.S. in 1844, for a tooth extraction. Nitrous oxide was further investigated by Humphrey Davy in 1800 at the Pneumatic Medical Institution in Bristol. Humphry Davy discovered the gas’s anesthetic properties when inhaled. Davy’s student, Michael Faraday, showed in1818 that inhalation of ether had the same effect.

In his book on nitrous oxide, Davy recorded that breathing the gas helped to relieve toothache – from which he was suffering at the time – and suggested: “it may probably be used with advantage in surgical operations.” But the pain-relieving properties of nitrous oxide were not explored any further until nearly fifty years later. Initially, society was more interested in nitrous oxide as a source of amusement and entertainment. What a waste of valuable time!

So the literature informed us that nitrous oxide was used alone, without any supplementary air or oxygen. In the latter part of the century, it was found that the gas mixture should comprise at least 21% oxygen by volume in order to avoid risks and side effects. In 1881 nitrous oxide was introduced for pain relief in childbirth. Then in 1911, the American anaesthetist, Arthur Ernest Guedel, described an analgesic technique where patients themselves were allowed to control the administration of a mixture of nitrous oxide and air during childbirth and minor surgery. In 1933, Dr R J Minnitt invented the gas and air machine which allow labouring women to breathe in a mixture of the nitrious oxide with room air, therefore, achieving a level of pain relieve, but not anaesthetising her to a point of losing consciousness.

In 1961, Michael Tunstall et al described for the first time the medical use of a pre mixed gas consisting of 50% nitrous oxide and 50% oxygen as an analgesic during childbirth. It was found that it was possible to store a homogeneous gas mixture containing up to about 75% nitrous oxide at a pressure of 132 bar, at ambient temperature. This led to the premixed gas patent – and to the entenox product introduced by BOC Medical. The machines used in hospitals today allover the world mix nitrous oxide gas with pure oxygen instead of room air.

Some interesting historical letters

Watts. G. (2011). Michael Tunstall. BMJ. Vol. 343:d4977
Callister, L. C., Khalaf, I., Semenic, S., Kartchner, R., Vehvilainen-Julkunen, K. (2003). Medscape

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