The East-Freeman Automatic Vent: An interesting footnote in the history of mechanical ventilation

An example of the East-Freeman Automatic Vent from Oxford was found in the early anaesthesia equipment collection at St George Hospital, Sydney. It weighs less than 200 g and is representative of a group of miniature ventilators that were described in the 1960s, including the Minivent from South Africa and the Microvent from Canada. All relied on a pressure-operated inflating valve that was described in 1966 by Mitchell and Epstein from Oxford. The ventilators were compact, portable and were powered by the gas supply from the anaesthesia machine or other driving source that distended a reservoir bag. The main problem was that they could stick in the inspiratory phase. This led to pressure in the lungs rising towards the driving pressure. There was a risk of barotrauma to the patient if the system was not promptly disconnected. While theyhad provided an alternative to hand bagging, they were superseded, as more sophisticated and safer ventilators became widely available.