Hippocrates, the father of medicine, is accredited as being the first to realise that the smell of a person’s breath could be used to establish what was wrong with them. He expected his students to be able to associate the sweet smell of rotten apples in a patients breath with diabetes, and a fishy, urine-like smell as an indicator of kidney failure.

As science and technology advanced, Lavoisier, the father of chemistry, began the process of systematically analysing the chemical constituents of gases. He was the first to recognise and name oxygen and the role it plays in combustion reactions. That led to his discovery of carbon dioxide in the air we breathe out, one of the products of respiration in which glucose and oxygen are turned into water, carbon dioxide and ATP – the organic energy carrier that drives muscle movement and intracellular energy exchanges.

The most commonly known breath analysis test of today is the breathalyser test, used to quickly determine whether a driver is ‘over the limit’ and therefore legally incapable of driving a vehicle. It is increasingly common for all employees and visitors to safety-critical worksites to be breathalysed, whether they are driving or not.

The test measures the percentage of alcohol in the breath a person exhales. This is used to accurately determine the amount of ethanol (CH3-CH2-OH) that is being carried in the blood. The accuracy of today’s breathalysers means that the readings are acceptable for prosecution, but a confirming blood test used to be (and sometimes still is) required.

This principle, that the constituent gases or volatile organic compounds (VOCs) that we breath out can be directly traced to substances in our blood, is true of all breath analysis equipment.

Hydrogen breath tests and gastroenterology

During the latter part of the nineteenth century, Linus Pauling’s milestone discovery of 250 unique substances present in exhaled breath offered promising insight into breath testing possibilities.

In 1970s the concept of lactose intolerance (LI) was evaluated using a hydrogen breath test. Newcomer and his associates studied poor lactose absorption by analysing breath for hydrogen (H2) and CO2. H2 was found to be elevated in lactose intolerant people, while CO2 values were below normal in most patients. The researchers determined that ‘measurement of breath hydrogen is sensitive and specific, and does not require ethanol or isotopes’ and argued that it would be a ‘most suitable test for population screening for lactase deficiency’.

Bond and Levitt then went on to use a breath H2 test to conclude that some disaccharide sugars remain ‘unbroken and unabsorbed’ in the small intestine due to incomplete digestion.

Many patients with digestion disorders are unaware of the relationship between diet and the symptoms they present. These include abdominal pain, bloating, flatulence and altered bowel movements (diarrhoea and constipation), irritable bowel syndrome or Coeliac/celiac disease. Such patients may have undiagnosed carbohydrate malabsorption or SIBO (Small intestinal bacterial overgrowth).

Bacteria in the bowel generally produce hydrogen gas on fermentation of their carbohydrates. Bacteria can only do this when dietary carbohydrates are not absorbed in the small intestine and, instead, stay as undigested material travelling into the large intestine.

Though some of the hydrogen gas produced by the bacteria is expelled as flatulence or in making other molecules, most of the gas is absorbed across the lining of the large intestine into the blood stream. The gas is then transported to the patients lungs, exchanged into the airways of the lungs and breathed out. The levels of hydrogen gas in the breath can therefore be use to determine if and how much bacterial fermentation is occurring in the bowel.

Hydrogen breath tests are, therefore, specific and sensitive diagnostic tests that can be used to either confirm or eliminate the possibility of carbohydrate malabsorption or SIBO in patients. The breath testing procedure is simple, reproducible and safe, an ideal substitute for more invasive, uncomfortable and expensive techniques traditionally used in gastroenterology.

Afrox has a key role to play in maintaining the accuracy, validity and credibility of breath test results from the equipment being use by gastroenterologists. The instruments are required to measure very small difference in H2 concentration and each system has to be calibrated before being used on patients.

The calibration procedure requires the use of a high quality calibration gas mixture containing 20 ppm of H2 in otherwise uncontaminated clean air. Gases such as these are available through Afrox Special Products, which provides precision gas solutions for optimum accuracy and control in specialised medical and laboratory applications.