At the start of World War I, relatively inexperienced physicians were responsible for administering anaesthesia to severely injured soldiers in shock. Lack of knowledge, experience and proper equipment led to high mortality rates. Based on his pre-war experience in the department of respiratory physiology at Guy's Hospital in London, the British physician Geoffrey Marshall was ordered to investigate the high mortality rates. He was one of the first physicians to systematically record blood pressure, heart rate and haemoglobin level. The anaesthetic techniques of the time resulted in deep hypotension and high mortality. Marshall's main achievement was his design of a machine which could be used to reliably administer a mixture of ether, oxygen and nitrous oxide. This led to much more stable anaesthesia and a substantial decrease in mortality. After World War I, his invention became known as Boyle's machine, providing a template for all subsequent anaesthetic machines.