John Snow (1813-1858): experimental studies on
rebreathing of anesthetic gases in exhaled air

Baum J.
Abteilung fur Anasthesie und Intensivmedizin,
Krankenhaus St.-Elisabeth-Stift, Damme.
Anasthesiol Intensivmed Notfallmed Schmerzther. 1995 Feb;30(1):37-41


As early as in 1850 (only 4 years after the first clinical performance of ether anaesthesia by W. T. G. Morton on 16 October 1846) John Snow recognised that ether and chloroform were exhaled unchanged with the expired air. To reuse these unchanged vapours in the following inspiration and thereby prolonging the narcotic effect of a given amount of anaesthetic vapour, he converted his ether inhaler into a To-and-Fro Rebreathing System: The apparatus was equipped with a facemask without an expiratory valve and a large reservoir bag containing pure oxygen; an aqueous solution of caustic potash was used as CO2 absorbent. In several experiments, performed on himself, Snow succeeded to demonstrate that rebreathing of the exhaled vapours was possible following carbon dioxide absorption, and that it resulted in a pronounced prolongation of the narcotic effects of the volatile anaesthetics. Furthermore, Snow performed experiments on animals using a closed system for evaluating the carbon dioxide production during anaesthesia. It is all the more worthwhile to introduce Snow's publications on these topics, as, despite their extraordinary theoretical and practical significance, they remained nearly unnoticed. Even in the fundamental articles by D. Jackson and R. Waters, both being the respected protagonists of the rebreathing technique in anaesthesia, the Snow papers remained uncited.
John Snow
Nitrous oxide
Inhaled anaesthetics
Obstetric anaesthesia
Molecular mechanisms
Chloroform anaesthesia
'The secularisation of pain'
John Snow and medical research
History of anaesthesia apparatus
John Snow and cholera epidemics
Consciousness, anaesthesia and anaesthetics

and further reading
Future Opioids
BLTC Research
Utopian Surgery?
The Good Drug Guide
The Abolitionist Project
The Hedonistic Imperative
The Reproductive Revolution
Critique of Huxley's Brave New World