A highly innovative advance in the design of anaesthetic breathing systems – 300-500 ml/min from 30g to 100kg.

Summary: The Humphrey ADE-circle system was developed as a highly-efficient multi-purpose anaesthetic breathing system for adults, children and veterinary use. Its unique design is significantly different from all other systems. In just one simple easy-to-use system it can be used for spontaneous, manual and ventilator respiration modes with or without a recycling soda lime canister.

There are two modes:

Significant advantages over the T-piece

• ADE-circle® uses up to 85% less of fresh gas flow:
   300 ml/min for a 3kg cat compared to
   1.5 – 2 litres/min for the T-piece
• ADE-circle® saves warm moist dead space gas
• ADE-circle®reduces pollution by using lower flows
• “PEEP” benefit – ADE-circle® keeps lung expanded
• Easy scavenging with ADE-circle® valve – no danger
   of twisting & causing airway obstruction
• Useful for exotic animals and birds
• Ventilator mode (hand & automatic)

Better design than other absorbers 

• Easily attached canister
• Soda lime lasts twice as long
• Effective & safe at minimal flows: 10 ml/kg/min = 300 ml/min
   for 30 kg dog
• Self-regulating exhaust valve – automatically recycles gas
• Hand ventilation without valve adjustment
• “PEEP” benefits
• No back flow & loss of fresh gas
• Refilling very simple – just pour & fill
• Ventilator mode (hand & automatic)


This versatile and simple-to use system covers the range that meets all requirements of a medical or veterinary anaesthetist for good safe anaesthesia.

It has won notable Design and Engineering Awards. Dr Humphrey was also awarded research prizes related to this system from the Royal college of Medicine and the Association of Anaesthetists’ of South Africa.

  • The innovative and unique 4-phase exhaust valve, unlike standard valves, stays closed at the beginning of expiration to automatically preserve all useful gases (dead space gas or gas for recycling) within the system while eliminating only alveolar gas. This significantly increases the efficiency of both the semi-closed and circle absorber modes of use over all other systems.
  • As a semi-closed system it not only combines into a single “easy-to-use” system the advantages of the T-piece, Mini-Lack, Lack, Bain without any of their disadvantages, but uses significantly lower fresh gas flows of up to 80%. It is twice as efficient compared with mini Lack, and 3-4 times more so than the T–piece and Bain systems. Pollution is similarly reduced.
  • As a circle system with a soda lime canister in the circuit, the position of the reservoir bag on the inspiratory limb (rather the common expiratory position of most absorbers) saves fresh gas (rather than expired gas). With the 4-phase valve it becomes uniquely efficient as it recycles dead space gas first before recycling alveolar gas.
  • The lever mechanism switches the system between the spontaneous, manual or ventilator mode without any other adjustment. As it weighs only 3kg, it is available World Wide by post from the website shop.

CLICK HERE to view Veterinary use.

CLICK HERE to view Medical use.

ADE-Circle QA Standards

isoceCE mark quality assurance

The ADE-circle system is manufactured to comply with all CE standards

Design technical standards

The Humphrey ADE-circle system conforms to British/European & ISO standards for 22mm & 15mm and weight-bearing connectors:- EN1281 & 2 incorporating BS 3849 parts 1 & 2 and ISO parts 1 & 2.


Shell Design Award: In 1985 the Humphrey ADE-circle system was awarded the prestigious Shell Design Award for excellence in design. The system remains essentially the same design today, but with several major improvements such as a new exhaust valve of especial benefit to children and small animals, plus a soda-lime recycling canister.

The Humphrey ADE-circle system also gained an Engineering Design Award in October 1999.


David HumphreyContinuing research

Dr David Humphrey, who trained in London and is a well known research anaesthetist. He has won two research awards for his work on the ADE system, one being from the Royal Society of Medicine, London. He is currently involved in research with sevoflurane in low-flow techniques, particularly in veterinary applications.

If you would like to invite him to lecture on “Safe, simple low flow anaesthesia” or contact him about any issue connected with the ADE-circle system or on low flow techniques, then please follow this link and select Enquiries and Support.

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