Background

The common practice when using inhalation agents for anaesthesia is to use an anaesthesia machine. The complexity of such a machine can vary greatly but consists in general of different systems integrated into one. An anaesthesia machine is in principal performing:

• control of composition of breathing gases to the patient e.g. supply of oxygen and anaesthetic agents.
• patient monitoring
• assisting breathing
• re-circulation of breathing gases to reduce consumption of anaesthetic agents.

To save anaesthetic gases a special circuit called a circle system is used which includes one way valves and a carbon dioxide absorber. The circle system allows exhaled gas from the patient to be re-circulated and the carbon dioxide absorber prevents carbon dioxide retention.

The AnaConDa replaces both the circle system and the vaporizer in an anaesthesia machine.

Due to the unique design of the AnaConDa only the anaesthetic agent is adsorbed by the conserving medium that is made of a form of active carbon. All other gases pass through and are evacuated through the exhaust on the ventilator. The miniature vaporizer can because of its big surface and its place close to the patient and using the heat from the patient vaporize any clinically relevant amount of isoflurane or sevoflurane
AnaConDa is also an excellent humidifier and contains a bacterial filter.

Comparison of AnaConDa to a circle system

AnaConDa		Circle system
Supply of vaporized anaesthetic agents		Supply of vaporized anaesthetic agents
Recycle anaesthetic agents		Recycle anaesthetic agent
Conserve anaesthetic agents		Conserve anaesthetic agent
No need for CO2 absorbers or one-way valves		CO2 absorber and one-way valves needed to prevent CO2 retention
Humidifies and filters the air		Need to add a humidifier and a filter to get optimal humidification and filtration
Vaporizes the anaesthetic agents		A vaporizer is needed

The AnaConDa has been tested for use in anaesthesia and found to save gases equal of using a circle system at fresh gas flows of approximately 1,2 l/min (1). So, by combining AnaConDa with a normal ventilator and a separate monitor system a low cost anaesthesia machine with the same performance characteristics as a modern low flow anaesthesia machine can be built.

1. Tempia A, et al: The anesthetic conserving device compared with conventional circle system used under different flow conditions for inhaled anesthesia. Anesthesia & Analgesia; Vol. 96, p 1056-1061, 2003.