Anaesthetic machine: fresh gas delivery units. II. Electronic units

Objectives: To analyse the design, functioning, benefits and drawbacks of e lectronic fresh gas delivery units (FGDUs) included in anaesthetic machines marketed in France in 1999. Data sources: Articles were obtained from a Medline(R) review (1980-1999; s earch terms: anaesthetic machine, flowmeter, vaporizer), textbooks and pers onal files; specific data were also provided by manufacturers. Study selection and data extraction: The articles were analysed in consider ing the differences between mechanical and electronic FGDUs. Data synthesis: Four anaesthetic machines out of 11 are equipped with elect ronic FGDUs. In comparison to mechanical units, they include the following benefits:wide range of accurate gas flow, especially in the tow flow range, with analog and digital display; intermittent delivery of each gas, which is essential for automated gas delivery and quantitative anaesthesia or tar get controlled (FET vapor) inhatational anaesthesia; facilitated oxygen rat io control; possibility to print the gas and vapor flows on the automated a naesthetic record; interruption of gas flow when the main switch of the mac hine is set to off; and absence of risk for retropollution. Three FGDUs out of four are adapted for gas delivery to an accessory (ancillary) anaesthet ic circuit. However, only one of them delivers a gas flow up to 30 L.min(-1 ). The specificity of the ADU AS/3(TM) (Datex-Ohmeda) is the bypass vaporiz er included in the FGDU with an exchangeable vaporizing chamber (cassette). The specificity of the Julian(TM) (Drager) is the delivery of fresh gas li mited to the expiratory phase during mechanical ventilation. The specificit y of the the FGDU from Kion(TM) (Siemens) is the possibility to act as an o pen circuit ventilator, similar to a Servoventilator(TM). The specificity o f the PhysioFlex(TM) is an FGDU included in the circle circuit, each gas an d liquid anaesthetic being directly injected into the circuit. Data from th e French medical device surveillance commission indicate that the main fail ures occur in the power supply device and the microprocessor. (C) 1999 Edit ions scientifiques et medicales Elsevier SAS.