Breath test

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A breathing gas test (also called breath test for short ) is a diagnostic procedure in which the exhaled air of a patient is analyzed . Areas of application are the detection of Helicobacter pylori with the 13C-urea breath test and intolerance of certain types of sugar (especially lactose intolerance ) with the hydrogen breath test or the inference of breathing gas concentrations on blood concentrations, for example when determining breath alcohol .

In principle, many respiratory gas tests work in a similar way: an initial sample of the exhaled air is taken, then a test substance is administered and then one or more additional samples of the exhaled air are taken. The different composition of the air before and after administration of the test substance can indirectly indicate certain pathological changes in the gastrointestinal tract.

Examples of respiratory gas tests

13 C-urea breath test

For the 13 C-urea breath test, the patient is urea administered, the (i.e., non-radioactive..) With the stable carbon - isotope 13 C is selected. A sample of the exhaled air is taken immediately before the urea administration and 30 minutes afterwards. In addition, shortly before the urea solution is administered, the patient is given an acidic drink in order to close the stomach door and thus ensure that the urea test solution remains in the stomach for as long as possible. If the patient is infected with Helicobacter pylori , the bacteria in the stomach wall break down the urea to form carbon dioxide (CO 2 ), among other things . This is exhaled and the proportion of 13 CO 2 in the total CO 2 before and after urea administration is determined with an infrared spectrometer .

Hydrogen breath test

In the hydrogen breath test, the hydrogen content of the basic exhaled air is determined first. Then the patient - depending on the question - is given a large amount of a certain sugar in an aqueous solution . The hydrogen content of the exhaled air is then determined again at short intervals (5–15 minutes). Bacteria present in the intestine are able to absorb and metabolize sugar. This creates gaseous hydrogen (H 2 ), which is exhaled through the lungs.

Alcohol test

The alcohol test determines the alcohol content in the exhaled air (e.g. with an Alcotest device). Since it is not possible to draw an exact conclusion from the alcohol concentration in the breath to the alcohol concentration in the blood without further information (see breathing gas analysis ), a blood test must be carried out for validation if an initial suspicion is confirmed .

See also

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