Hydrogen (H2) is a colourless, odourless and lightest of all gases, it is also the most abundant element in the universe¹. Methane (CH₄) is a chemical compound comprising of one atom carbon and four atoms of H2. Both H₂ and CH₄ are produced in the human digestive system.

Breath H₂ and CH₄ are used as a non-invasive, safe alternative to procedures such as biopsy to evaluate bloating, diarrhoea, constipation and malabsorption. In the 1970s and 2006, research found that approximately 35% of healthy adult subjects are CH₄ producers². Other research also found that 34% of patients with lactose intolerance who showed a negative H₂ breath test, showed an increase of CH₄ percentage of greater than 100%³.

From the document: MKT467 issue 4 The importance of breath holding and end-tidal samples for accurate breath testing.

References:

1. Hydrogen [Internet]. Royal Society of Chemistry. [Cited Thursday 20th February 2025]. Available from: https://periodic-table.rsc.org/element/1/hydrogen

2. Levitt MD, Furne JK, Kuskowski M, Ruddy J. Stability of human methanogenic flora over 35 years and a review of insights obtained from breath methane measurements. Clinical Gastroenterology and Hepatology. 2006 Feb 1;4(2):123-9. PMID: 16469670. DOI: 10.1016/j.cgh.2005.11.006

3. Strocchi A, Corazza G, Ellis CJ, Gasbarrini G, Levitt MD. Detection of malabsorption of low doses of carbohydrate: accuracy of various breath H₂ criteria. Gastroenterology. 1993 Nov 1;105(5):1404-10. PMID: 8224644. DOI: 10.1016/0016-5085(93)90145-3

From The Importance of Breath Holding and End-tidal Samples for Accurate Breath Testing.

No, hydrogen methane breath testing (HMBT) is completely non-invasive and painless. HMBT involves simply breathing into the device at specified intervals after consuming a test substrate.

The testing process usually takes a few hours, during which the patient breathes into the device at regular intervals following substrate consumption.

• Carbohydrate intolerance
• Carbohydrate malabsorption
• Intestinal bacterial overgrowth
• Investigation of intestinal transit time

From the manual: Gastro+ manual - 'Introduction' section

• Carbohydrate breakdown defiency
• Carbohydrate malabsorption
• Lactose intolerance
• Bacterial overgrowth
• Determination of time of passage through gut

From the manual: GastroCHECK Manual - 'Intended Use' section

When a patient comes in for a hydrogen methane breath test (HMBT), after recording their baseline results, the patient will digest a specific substrate which is metabolised by the bacteria in the small intestine which will start producing hydrogen (H₂) and/or methane (CH₄) gas. H₂, CH₄, and oxygen (O₂) will then be monitored in intervals; the O₂ measurement is important because it helps to ensure that the bacteria in the large intestine, rather than those in the mouth or stomach, are responsible for any gas production observed during the test.

The Earth’s atmosphere consists of around 78% nitrogen (N₂), 20.9% O₂, 0.93% argon (Ar), CO₂ 0.03%; with the rest being various gases¹. When you breathe in, your body converts a percentage of O₂ into CO₂, which settles at the base of the lungs, known as an end-tidal sample. During HMBT, if the levels of O₂ exceed 14%, it indicates that an end-tidal sample has not been achieved, likely due to dilution by dead space in the upper airway. In such cases, the GastroCH₄ECK^® device compensates for this discrepancy with a correction ratio which will be displayed on the screen.

Read the article here.

References:

1. The atmosphere [Internet]. National Oceanic and Atmospheric Administration. [Cited Thursday 20th February 2025]. Available from: https://www.noaa.gov/jetstream/atmosphere

Physiologically the mechanism for this is simple diffusion, from high concentration to low concentration. The alveoli are microscopic air sacs within the lungs, each of which has a wall that is only one cell thick (Figure 1). A net of capillaries surrounds each alveolus, and they also have walls which are only one cell thick. They are so narrow that red blood cells must go through them stacked up in line, one at a time carried by plasma.

When blood enters the capillaries of the lungs, haemoglobin on the red blood cells is loosely bonded with carbon monoxide (CO), which is picked up from the body's cells and the plasma carries the hydrogen (H₂) and methane (CH₄). Inside each alveolus, there is oxygen (O₂) which has been taken in by inhaling the air outside the body. The concentration of O₂ is greater in the alveolus than in the blood at this time, and the concentration of H₂ and CH₄ is greater in the blood than in the alveolus. Therefore, haemoglobin and plasma release the H₂ and CH₄ and it diffuses directly through the cell walls of the capillary and the alveolus, into the lung in parts per million (ppm).

When you exhale, the H₂ and CH₄ in the lungs are flushed out therefore holding the breath allows more of these gases to diffuse into the lung. They will continue to diffuse into the lung until they reach the same level as that in the haemoglobin and plasma thus reaching ‘equilibrium’.

Research has shown that the time point at which H₂ and CH₄ concentrations in the breath flatten or equilibrate to that in the blood is between 15-20 seconds^1,2.

Therefore Bedfont^® have selected a 15-second minimum breath hold required for accurately measuring H² and CH⁴ concentrations in the breath as this allows the gases in the lung to equilibrate and is also not too long to become uncomfortable for patients to perform the test.

From the document: MKT467 issue 4 The importance of breath holding and end-tidal samples for accurate breath testing.

From The Importance of Breath Holding and End-tidal Samples for Accurate Breath Testing.

The correction factor corrects any diluted breath sample if any excess oxygen (O₂) percentage is present in the breath sample than required. For example, a good sample is considered to be an end-tidal sample where the O₂% should be low. If the sample is diluted, then it is corrected by the correction factor to give exact concentrations of hydrogen (H₂) and methane (CH₄) in the breath sample.

Read the article here.