Equipment Setup and Use

•             ADE-circle system

•             Free-Ox Anaesthetic machine

The Humphrey ADE-circle system

A multipurpose delivery system for patients weighing from a few grams up to 150kgs.

•             Assembly

•             Leak test

•             Fresh gas flows for veterinary use

•             Fresh gas flows for medical use

Congratulations on visiting this page to set up your new ADE-circle system. Learning how to use new apparatus often causes concern for the safety of the user and patient. The commonest comment on the ADE-circle system is that it is so simple and easy to use with minimal nurse training. This were two of the three main goal behind the design – simplicity, safety and economy. Indeed the system was designed by Dr Humphrey for completely untrained lay staff while working in mission hospitals in Africa.

For those who feel the need for a demonstrations, this really not necessary. So be confident from the start. A simple chart is provided to act as a guide for the newcomer.

The information below is designed to help you set the system up in about 5 minutes and to use it with confidence. The basic information is here, but a frequently asked (FAQ) section is available on this website for reference. If you need help, please contact us on out international website address

The ADE-circle system is supplied complete in a box almost ready to use. You will find the metallic main body, the plastic soda-lime canister for recycling anaesthetic gas, reservoir bags, connectors and breathing tubes. These need assembling.


Basic anaesthetic machine required:

It is assumed that you have a basic standard anaesthetic machine with a flowmeter, vaporizer and fresh gas outlet. As the ADE-circle commonly uses very low fresh flows (FGF) of only 300-500 ml/min, the flowmeter must be calibrated for low fresh in increments of 100ml/min up to 1 litre/min, with top flows of over 5 l/min. The vaporizer must also be temperature and flow compensated to allow accurate delivery of vapour again at low flows of 300 ml/min. The fresh gas outlet must conform to the International Standard with a 22mm male tapered cone. The female inlet marked “FRESH GAS ONLY” on the ADE main body will directly slide on this cone and should be secured with a final push-and-twist action. If your machine has a non-standard outlet, then the ADE-circle system can be connected to a post or pillar on the machine (or even a drip stand) with a clamp kit (see spares).

Attachment of the ADE main body.

The main body is simply attached by a “push-and-twist” fit over the fresh gas outlet on the machine. Check with a gentle pull that it is secure and won’t fall off. If the fresh gas outlet has a groove in it for an “O” ring, a locknut can be used to secure the ADE to the machine. This is automatically provided on the Free-Ox machine.

Reservoir Bags:

Three sizes of reservoir bags are supplied, namely 1/2, 1 and 2 litre capacity. These bags connect to the ADE main block on the male cone engraved “RESERVOIR BAG ONLY”.

Notes: The bag for any patient needs to be twice the tidal volume. In medical practice this is about 7 ml/kg and in animals it is about 10 ml/kg. Thus any patient under 10 kg requires the ½ litre bag. Simply for convenience the one litre bag is used for patients between 10 and 50kg, and the 2 litre bag for patients weighing between 50-150 kgs.


Two 15mm smooth bore tubes are supplied and can be used for all patients. Connect the 15mm straight blue connectors into one end of each tube, and push the other ends firmly over the “Y” patient connector. Connect the 15 mm connectors into the male cones of the ADE system. Two right-angle bend connectors (supplied) are helpful as the tubes then hang down, reducing the stretching of tubes at their attachment to the ADE system.

Important Notes: These are smaller than normal but are suitable for all patients. These tubes are specially made with an inner bore being smooth on the inside, with a re-enforcing outer ring to allow bending without kinking. The smooth tubes allows gas to flow very easily along the tube with minimal resistance. Do not be tempted to use standard corrugated tubes of the same size as these are four times more difficult to breathe. Re-order tubes from Anaequip.

The system is ready for use in small patients under 7kg.

Soda lime canister:

Filling the canister: This canister needs filling with soda lime before use. Remove the lid on the base by undoing he four thumb screws, cover the four exposed screw holes and pour in the soda lime granules, making sure that no granules get into the screw holes. The canister must be filled to capacity otherwise it will not absorb carbon dioxide efficiently.

Connecting to the patient; if the patient weighs more than 7kg, connect the soda lime canister by pushing it over the two male cones of the ADE main body as far as it will go. Locate the two metal locking nuts on the male cones of the ADE main block and slide them over the canister connections. Carefully catch the thread and tighten. Take care not to cross-thread the lock nuts – this damages the connection and leaks will occur. Re-connect the tubes to the red and blue valves of the canister.

The system is ready for use in small patients over 7kg.

Important Notes: The soda lime canister is used to recycle gas by absorbing the carbon dioxide added by the patient to expired gas. Recycling becomes increasingly cost-effective the larger the patient, a starting point being over 7kg. Under this mass do not use the canister and follow the fresh gas instructions detailed below. Patients over 7kg can easily breathe through the canister.

If a granule does get into the screw hole, it must be removed otherwise the lid will not seal tightly and the canister will leak with the possibility that the patient will wake up! Use a pin to get it out or turn the canister upside-down and start again.

Some soda lime grades are better than others. Round granules of even size are best (eg Intersurgical Spherosorb) and work well. Irregular soda lime granules are less efficient as large gaps can occur with poor efficiency. Never use the dusty remnants in the supplier’s canister – it clogs the system and is toxic if breathed in.

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Once set up as described above the system needs to be leak tested before it is ready for use. If the system leaks, the reservoir bag won’t fill despite high fresh gas flows and worse still the patient wakes up!

Leak Test:

Test your machine first by putting your finger over the fresh gas outlet, pressurize the system against your finger by turning the gas on – then turn it off and see if the pressure against your finger holds for 3-4 seconds. If not, your machine itself leaks and must be serviced.

Next connect the ADE system without the canister and tubes to the anaesthetic machine. Press oxygen flush to inflate reservoir bag by blocking inspiratory limb with your finger – does bag stay inflated? If not, the leak is in the bag.

Attach the ADE tubing. Screw down the exhaust valve. Press oxygen flush to inflate reservoir bag by blocking the tubing at the “Y” piece with your finger – does bag stay inflated? If not, the leak is in the tubes.

Attach the canister and tubes. Screw down exhaust valve. Press oxygen flush to inflate reservoir bag by blocking the tubing at the “Y” piece with your finger – does bag stay inflated? If not, the leak is in the canister. See FAQ for more details on resolving leaks.

For a complete leak test guide, please download below:

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Fresh gas flows for Veterinary use:

A chart has been prepared to assist in using the system economically. These recommended FGFs are much lower than used with other systems which waste significant amounts of oxygen and vapour. The system really does use much lower fresh gas flows. The design is quite different from ALL others; the major innovation is the addition of a 4-phase exhaust valve (see the website “Vet Applications” menu for more details). Using fresh gas flows above these recommendations just waste gases, cost more, cause pollution and, worse still, compromise the patient by washing out warmed humidified gases which keep the patient warm! Try them out and become confident – but the system must be leak proof (see leak test above)! Those who still use nitrous oxide are advised to read the notes on the chart concerning minimum oxygen requirements.

Download the chart, print it on an A4 page, fold it in half along the split on the chart for “7kg and under” and “over 7kg up to 100kg” and laminate it. Punch a hole in one corner with a paper punch, pull a rubber band through the hole and loop it back on itself – and hang the chart with the ADE system.

The chart is split into two sections with the FGFs for use with small animals 7kg or less used as a semi-closed system, and those for larger animals over 7kg used with the soda lime canister. Fresh gas flows and the percent of vapour required are higher at the beginning of anaesthesia than for maintenance after the desired level of anaesthesia has been achieved. The chart defines “Induction” and “Maintenance” fresh gas flows related to the weight of the patient. The third column defines slightly higher fresh gas flows for compromised animals or those that have no analgesic in their premedication.

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Fresh gas flows for Medical Use:

For children under 10kg, the system is used in the semi-closed mode without the absorber (similar to the T-piece or Bain system). Fresh gas flows are set at about 2 l/min during induction, and reduced to 1.5 l/min for maintenance.

For adults, attach the absorber and induce with fresh gas flows not more than 2 l/min. Reduce FGFs to 300 to 500 ml/min once a steady state is achieved. See notes below.

Notes: The main clue to a successful and quick anaesthetic is to pre-fill the system with oxygen and the vapour at a percent about 1.5 to 2 times the anticipated maintenance level eg 2.5 – 3% for isoflurane and 4-5% for sevoflurane. Once the level of anaesthesia has been reached, lower the FGFs to those recommended.

If a rapid change is required in the depth of anaesthesia (deeper or shallower), squeeze the bag to empty it, adjust the vaporizer and refill the reservoir bag rapidly by turning up the FGF. Reduce the FGF once the bag is full. Sevoflurane is very fast to respond to such changes – be careful not overdose.

For information on how the system achieves its efficiency, refer to information under Vet Use section.

Humphrey “Free-Ox”, “Pack-flat” Mini-portable, and Wall-mount anaesthetic machines

All instructions are included with the anaesthetic machines.

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