The amazing Minivent ventilator

Abstract

In the mid-1960s Dr Anthony Cohen, an anaesthetist in private practice in Johannesburg, developed the Minivent respirator in response to the lack of ventilators that existed at that time in operating theatres in both private and state hospitals. The remarkable, rugged, miniature ventilator had only four components, could fit into an anaesthetist’s pocket and required no electrical power source. The pressure generated by the distension of a reservoir bag by the flow of anaesthetic gases to the patient triggered inspiration and the switch from inspiration to expiration was controlled by a pressure-sensitive magnetically operated bobbin. The device operated as a minute volume divider. Respiratory rate was obtained by counting the clicking noise from the bobbin and, provided there was no leak, tidal volume was easily calculated by dividing the gas flow by the respiratory rate. The device was widely used in numerous countries including South Africa, the United Kingdom, Australia and Canada.

Keywords: anaesthesia, history of anaesthesia, medical equipment, ventilators