|Dr John Snow (1813-1858)
Dr Snow made the first documented attempt to assess anaesthetic depth in 1845. He described five levels of anaesthesia with progressive impairment of mental function and voluntary movement, until surgical anaesthesia was reached. The fifth degree was characterised by weak, irregular respiratory movements and was described as the stage preceding death.
He is also reputed to have administered chloroform to Queen Victoria, for the birth of Prince Leopold in 1853 and later for the birth of Princess Beatrice in 1857.
Dr Arthur E. Guedel (1883-1956)
In 1937, Dr Arthur E. Guedel refined this system and developed a chart classification of ether anaesthesia based on lacrimation, pupil size and position, respiratory pattern and peripheral movement. This method of staging was designed to avoid the hazards of too deep anaesthesia.