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Hydrogen Breath Test.

Principles of the hydrogen breath test

The purpose of the procedure is to examine the hydrogen content of our exhaled air.  The test is a non-invasive method for determining certain digestive processes based on the premise that hydrogen occurs in our system only as the result of bacterial fermentation of carbohydrates.  The pathological breakdown of certain sugars (the so-called disaccharides) causes hydrogen gas to form in our bowels and it is this that this method will show. The results obtained can provide information about diverse conditions, depending on the test material used.

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Most frequently used test materials

  • lactulose
  • lactose
  • glucose
  • fructose

Under normal conditions, the hydrogen gas concentration of the exhaled air is extremely low, <20 ppm (pars per million).  We use a gas chromatography to analyze the contents.  The test material consumed by a patient gets forwarded undigested from the small intestine into the large intestine - either badly absorbed or not absorbed at all – where various gases, including hydrogen, are formed as the result of bacterial fermentation and accompany the breakdown process.  The hydrogen passes through the intestinal wall, gets into the blood stream and into the lungs from where it later appears in the exhaled air.

The examination consists of checking the hydrogen content of our breath just before consumption of the test material and then periodically thereafter.  If the results are higher than normal, then the carbohydrate digestion is not adequate.

Hydrogen breath test with lactulose

The hydrogen breath test with lactulose is used for determining the time it takes for food to travel through the small intestine (intestinal orocaecal transit time) as well as the indirect diagnosis of excessive bacterial growth (contaminated small bowel syndrome).

Lactulose is a disaccharide, a sugar derivative that only bowel bacteria can breakdown and, since the digestive enzymes of the small intestine cannot break them down, they arrive in the large intestine practically unchanged.  Its effect is exerted in the large intestine where, due to the impact of bowel bacteria, short-chain carboxylic acids - lactic acid and acetic acid followed by, methane gas and hydrogen gas - develop as a result.   

Evaluation of the examination results:  the time needed for the food to pass through the small intestine, the transit time, is obtained by the time it takes for a change in concentration above 20 ppm to appear.  The normal transit time may be obtained by examining a healthy control group.  The average time is generally 120 minutes.  If the hydrogen breath test with glucose is also abnormal, showing a shorter time than that of the control values, it signifies bacterial contamination of the small intestine  If normal, we measure the transit time.

Hydrogen breath test with lactose

The hydrogen breath test with lactose (a disaccharide made of glucose and galactose found in milk) is used for diagnosing lactose intolerance.  The lactase enzyme produced by the intestinal epithelial cells in the jejunum brakes the lactose down into glucose and galactose that get absorbed into the blood stream.  If no lactase enzyme is produced, then the lactose is broken down into hydrogen and organic acids after bacterial fermentation.  Significant measurable hydrogen concentration in the exhaled air is indicative of lactose intolerance.

Evaluation of the examination results:  in the case of normal transit time in the small intestine, if 90-120 minutes after ingesting the lactose solution the change in hydrogen gas concentration measures above 20 ppm, this indicates lactose intolerance.            

The examination may also be periodically supplemented with a blood glucose test.  In the case of normal break down, following the ingestion of the lactose solution, glucose and galactose will form and get into the blood stream.  The liver will turn the galactose into glucose which will again get into the blood stream thereby raising the glucose concentration level in the blood.  Periodic blood glucose tests help in evaluating the measure of lactose break down.  In cases of lactose intolerance, blood glucose concentration does not change significantly while, in normal lactose break down, the blood sugar is raised to the appropriate level.

Hydrogen breath test with fructose

The vernacular refers to two disorders when dealing with fructose intolerance, thus, it is important that we first clear the concept.  The exact name of one of the disorders is Hereditary Fructose Intolerance which is a very rare but serious disease with an occurrence rate of 1:20000-1:40000.  Fructose is absorbed in the bowels, but in individuals affected with HFI, the special enzyme in the liver that would turn it into glucose is missing causing an accumulation of fructose resulting in the following symptoms: low blood sugar, somnolence, cramps and later, liver and mental damage.  The disorder is diagnosed through a blood test and liver biopsy.  The symptoms usually appear once infants stop breast feeding making diagnosis possible in early childhood.  HFI is easily treated with a fructose free diet.

The other fructose intolerance disorder is fructose malabsorption which a much more frequent occurrence than the hereditary form and not found only in children.  In this case, for various temporary or permanent reasons, the fructose is neither broken down nor absorbed in the small intestine causing it to get into the large intestine where the bacteria ferments it.  As a result, acids and gases are formed causing bloating, abdominal pain and diarrhea.

Weakness, tiredness and anemia may result.  Treatment consists of staying away from foods containing fructose.  The hydrogen breath test is good for identifying this type of fructose intolerance.

The testing procedure

The test should be conducted in a location with clean air on an empty stomach (min. 6 hours of fasting).  There should be no cigarette smoking or foods or drinks containing mint (i.e., chewing gum, candy) consumed for 12 hours preceding the test, nor brushing of teeth with toothpaste.  The oral cavity and pharynx should be disinfected by rinsing with a disinfectant solution or by gargling.     

After the initial hydrogen breath test taken on an empty stomach, the Patient will be asked to drink 300 ml of water containing 20 gm lactulose or 75 gm carbohydrates (lactose, glucose, fructose), following which the breath test will be repeated every 20 minutes during 120 or 180 minutes.  The hydrogen content of the exhaled air will be measured and the measures evaluated.  Evaluation:  the correlation of the hydrogen gas with the basic concentration values is evaluated.  A value of >20 ppm indicates an abnormal condition.

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