StandardsThe Humphrey "FREE-OX" anaesthesia and critical care machine
New technology reducing costs and eliminating oxygen cylinders from veterinary practice. (Jan 27th 2007)
Summary
A new anaesthesia and critical care machine, the Humphrey “Free-Ox”, has been developed in South Africa and takes advantage of the extraction of oxygen from air by an oxygen concentrator. The latter provides oxygen (93%) for many thousands of hours at almost no cost, and is now very reliable and easy to maintain. The monthly costs of cylinder rental and refilling are thus eliminated. The “Free-Ox” anaesthetic machine incorporates the Humphrey ADE-circle anaesthetic breathing system which uses minimal maintenance flows of only 500 ml/min for all animals; this results in a significant saving of isoflurane and sevoflurane. When not used for anaesthesia, the machine can be used for critical care oxygen therapy which has previously been prohibitively expensive when using cylinders. The “Free-Ox” machine thus adds a new cost-effective dimension to anaesthesia and critical care, saving on oxygen and anaesthetic vapours. On connection to a mains electrical source, it is immediately ready to use.
The Humphrey “Free-Ox” anaesthesia and critical care machine: This machine has been designed to use the advantages of an oxygen concentrator and also to reduce the cost of vapour by using the Humphrey ADE-circle system (ref 1, 2). The concentrator weighs about 27kg and is about the size of a small under-counter fridge – running with as little noise. It neatly fits within the main frame of the anaesthetic machine. The oxygen outflow from the concentrator is fed by a hose to the inlet on the back of the anaesthetic machine. The supply to this inlet is easily switched to a reserve oxygen cylinder should there be a power failure. The “Free-Ox” machine uses a Devilbiss concentrator which is well built and strong enough to supply oxygen to a second machine provided the total flow does not exceed its capacity of about 5-6l/min.
Fig 1: The “Free-Ox” anaesthetic machine the oxygen concentrator (on wheels) fits into the trolley frame and supplies 93% oxygen to the flowmeter at up to 5 litres per minute. The new Penlon vaporizer supplied (isoflurane or sevoflurane) has a 10 year service interval. After induction, the Humphrey ADE-circle system only requires a flow of up to 500 ml/kg/min.
Cost of oxygen
Up to now vets have had little choice but to buy oxygen in cylinders, locking them into monthly rental and refill costs. In New Zealand oxygen costs vary greatly but tend to be between $100, $150 and $250 per month for a small, medium or large practice. Sadly the smaller the practice, the greater the cost of oxygen as smaller cylinders cost more! Other disadvantages of cylinders are that they run out and during a longer holiday weekend or over Christmas this is not good news; in more remote environments it may be some days before new cylinders are delivered – incurring yet another charge for delivery. Although it might save lives, oxygen therapy for sick animals is prohibitively expensive. Finally oxygen cylinders are heavy and can result in staff injury. Not surprisingly the aim of the “Free-Ox” machine was to eliminate all these problems. It does just that with the inclusion of an oxygen concentrator!
The Humphrey "Free-Ox" anaesthesia and critical care machine
Author: Dr David Humphrey, MBBS (London),
DA (S. Africa)
University post: Medical Anaesthetist & Senior
Lecturer, University of Natal (1978-1995)
Address: 303 Davenport Road, Glenwood, Durban 4001,
South Africa
Contact: Tel/Fax 031-2022552, Email: david@anaequip.com