Breath Analysis in Veterinary Medicine
18 March 2004
For centuries, doctors dealing with human patients have known that certain odours on the breath are a good indicator of a particular disease - such as the pear drops smell on the exhaled air from a person with diabetes. But normal human breath can contain at least 3000 different gases and changes in the concentration of some of these components may be useful in the diagnosis of a wide range of disease conditions.
The technology is now available to accurately analyse this complex mixture in the laboratory and these methods are likely to be especially useful in the veterinary field, according to Dr Cathy Wyse and her colleagues at the Institute of Comparative Medicine, writing in this week's Veterinary Record (March 20, 353-360), the official journal of the British Veterinary Association (BVA).
Many current methods for diagnosing disease in animals may be stressful for the animal, such as taking blood samples or skin biopsies. Other methods such as x-rays and ultrasound may require the animal to face the risks involved with a general anaesthetic. But to collect a breath sample a dog or horse need only wear a face mask for a few minutes, while cats and smaller animals can be briefly put inside a closed chamber.
"The greatest advantage of the breath test over other diagnostic methods is the ease with which it can be carried out - breath samples can be collected anywhere and by people with no medical training," Dr Wyse explains. "The non-invasive nature of the breath test makes it a particularly attractive diagnostic method in veterinary medicine."
Three main methods for using breath samples in diagnosis are currently under investigation by medical and veterinary scientists. Some tests will directly measure the gases in a patient's breath while others will analyse the chemicals dissolved in the fluid that condenses out when the breath is cooled. A third type of test will recover the isotopes of carbon produced after the breakdown of a radioactive-labelled substance swallowed by the patient just before the test. This latter method is the basis of the Carbon 13 test used to diagnose people with a type of bacteria (Helicobacter pylori), which causes gastric ulcers. At the moment this is the only breath test for medical purposes in routine use.
But Dr Wyse says the technologies for carrying out these analyses - mass spectrometry, gas chromatography and various forms of biosensor - are rapidly becoming cheaper, more portable and easier to use. That is largely because of the interest from environmentalists in using this equipment to control air pollution, but it can easily be adapted for medical use.
Eventually it is hoped that the equipment will become so simple and portable that it may even be possible to put it in the boot of a vet's car as he or she goes out on a routine visit. But in the meantime there is a lot of basic science to be carried out - such as working out the 'reference ranges' for each particular component in the breath that will be used to distinguish between health and sickness in individuals of each animal species.
Notes for Editors:
- For further information please contact Chrissie Nicholls or Helena Cotton in the BVA Press Office on 020 7636 6541 or email chrissien@bva.co.uk.