Michael Tunstall

BMJ 2011; 343 doi: (Published 03 August 2011) Cite this as: BMJ 2011;343:d4977
  1. Geoff Watts, freelance journalist, London
  1. geoff{at}

Innovative obstetric anaesthetist responsible for Entonox

As recently as 50 years ago the adequacy of pain control in childbirth could still be something of a hit or miss affair. That things began to improve in the 1960s owes much to the ingenuity and persistence of Michael Tunstall, an unassuming specialist in obstetric anaesthesia whose name is less familiar than it deserves to be. It was his determination that gave medicine the half and half mixture of the gases nitrous oxide and oxygen, generally known by its tradename Entonox.

Before the advent of Entonox, pain relief in labour was mostly by nitrous oxide mixed with 50% air. This, according to Felicity Reynolds, emeritus professor of obstetric anaesthesia at St Thomas’ Hospital in London, was unsatisfactory. “Even when the equipment was working properly you only got 10% oxygen. But often it didn’t work well, and you might get too much air and not enough pain relief. Or too much nitrous oxide and even less oxygen.”

“Poynting” out a solution

The obvious remedy, a pressurised cylinder of premixed nitrous oxide and oxygen, was viewed as unfeasible. Oxygen in cylinders is normally a …

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