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Departments & Programs,UW Hospital and Clinics,Pulmonary Diagnostic Lab

Breath Hydrogen (BH2) Testing Policy and Procedure

Breath Hydrogen (BH2) Testing Policy and Procedure - Departments & Programs, UW Hospital and Clinics, Pulmonary Diagnostic Lab


Principal and Purpose

Breath Hydrogen (BH2) Testing is the gas chromatographic measurement of Hydrogen (H2) and Methane (CH4) from exhaled gas. The rationale is to serve as a non-invasive monitor for the assessment of dietary intolerance to complex sugar and/or disaccharide ingestion.

When bacteria digest (or ferment) carbohydrates, they produce acids, H20 and gases. The major gases which are produced include carbon dioxide (CO2), hydrogen (H2), and methane (CH4). If there is impaired digestion of disaccharides of complex carbohydrates, of if the conditions of mucosal health or transit time do not permit efficient absorption of simple sugars, or if fecal flora are colonizing the superior portion of the gastrointestinal tract, carbohydrates will come into contact with fermenting bacterial flora and H2 and / or CH4 will evolve. The majority of these gases will be eliminated as flatus, but 14-21% will be absorbed into the bloodstream and be eliminated by the lungs.

By collecting a patient's expired gas and analyzing for the presence of H2 and / or CH4, the clinician is able to monitor the completeness of absorption of oral carbohydrate loads.


The Pulmonary Diagnostic Lab Technologist shall perform a calibration of the Quintron model SC Microlyzer prior to testing.


Signed or electronically generated physician request.
Pulmonary Lab BH2 data sheet.


BH2 testing is indicated in patients whose clinical history is suggestive of:

BH2 testing may be used to aid in the gastrointestinal diagnosis in patients:

Limitations and caveats in the application/interpretation of H2 breath analysis test include:


Instrument Calibration:
The Quintron Model SC Microlyzer is calibrated with known concentrations of H2, CO2 and CH4.

  1. The instrument power is on for a minimum of 4 hours and the pump should be running for a minimum of 40 minutes prior to instrument calibration.
  2. Room air is analyzed and values are adjusted to read zero.
  3. A sample of calibrating gas is introduced using a 30 ml plastic syringe by attaching the syringe to a calibration gas canister with a stop cock.
  4. The calibration gas is immediately introduced into the Microlyzer using a slow injection method.
  5. Once values have stabilized, the display is adjusted to the appropriate gas concentrations which are displayed on the cylinder.
  6. Repeat this process an additional time to assure accuracy (repeatability) of the calibration gas analysis. Note: This process should be repeated every hour if the analyzer cal is suspect (drifting, zero problems) and if the test exceeds 2 hours - to adjust for the inherent electronic drift of the instrument.

Patient Preparation, Sample Acquisition and Analysis:

  1. The patient should be instructed to fast for 12 hours with no food and only water to drink before the test. Avoid gas producing food (such as beans) the day before the test.
  2. The patient should not smoke, sleep nor exercise vigorously for at least one half hour before or anytime during the test.
  3. Ask the patient about any recent antibiotic therapy as this can affect the test. The physician should also be made aware of such treatment.
  4. Explain the collection procedure to the patient and or the patients' guardians if the child is not old enough to understand.
    • Expirate is obtained in a gas collection device via a low resistance one-way valve mouthpiece or mask system. Demonstrate to the patient how to exhale into the mouthpiece. Caution the patient not to take in a deep breath prior to exhalation (end - expiratory sample).
    • With infants or neonates who cannot cooperate, contamination of the alveolar sample may be seen. Collection of the sample may involve the use of a tight fitting face mask and one-way valve system in order to collect only expired gas. Note: Hyperventilation by a strongly crying infant or neonate may alter collection values.
  5. As H2 is the most diffusible of all gases, storage of the expired gas sample must be in a vessel that will prevent the loss of H2 concentration. Gas bags of Mylar impregnated foil or evacuated rubber topped glass tubes may be used.
  6. The expired gas sample should be introduced in to the analyzer per manufacturer's specifications (Quintron Model SC microlyzer, which operates under the principles of gas chromatography). Record the baseline corrected H2, CH4 and CO2 levels on the BH2 worksheet.
  7. Various concentrations of carbohydrate can be mixed in water from the patient to drink. Administer the appropriate dose of (lactose, sucrose, glucose, fructose to the patient. Patient should ingest the carbohydrate relatively quickly, preferably in less than a 30 minute period.R

    Recommended Dosages

    Requesting physician can specify a lower dose (glucose, lactose, sucrose, fructose).

    Children (up to 25kg body weight): 1 gram/kg up to 25 grams-dissolved in 8 ounces of water.

    Teens and Adults: 2 grams/kg -up to 25 grams total

    25 grams of lactose for lactose intolerance/malabsorbtion - dissolved in 9 ounces of water.

    Bacterial overgrowth study: 50 grams of glucose dissolved in 8 ounces of water.

    Intestinal transit time: 10 grams lactulose dissolved in ½ glass (4 oz) of water. (Application: Looking for ability to generate hydrogen if other tests are negative)
  8. A baseline H2 is commonly less than 10 ppm.
    • Higher values for H2 may indicate incomplete fasting prior to the test, ingestion of slowly digesting foods the day before, or (if the level exceeds 20 to 30 ppm) the presence of bacterial overgrowth in the small intestine.
    • A positive response is an increase of at least 20 ppm at any given point in the sampling period of the H2 gas from the lowest point measured.
      • If the breath hydrogen level increases by at least 20 ppm and is accompanied by reports of discomfort and/or diarrhea. The test may be interpreted as intolerance. If the H2 is increased without being accompanied by symptoms, the condition may be called carbohydrate malabsorption.
      • If the breath hydrogen does not increase by 20 ppm in patients, the possibility of a false negative test should be considered.
    • Such results may be seen in the presence of severe diarrhea or recent administration of antibiotics and if the patient has not fasted properly before the test, or smokes or eats during the test.
  9. Methane (CH4) is not commonly seen, but it can be normal to have up to 6 to 8 ppm. If both the H2 and the CH4 are increased after the carbohydrate challenge, the 2 responses should be summed to estimate the degree of malabsorption. If the sum of the increased H2 and CH4 is equal to, or greater than 20 ppm the test may be considered positive.
  10. Alveolar gas samples should be collected and analyzed every 30 minutes for up to 2 hours or if a physician deems an extended length necessary.
  11. Results should be recorded on the Pulmonary Lab BH2 data sheet.
    • Baseline and peak values should be posted in the Jaeger system and sent to WISCR-IT (parameters only) when testing is completed.
    • A paper copy should also be sent to Medical Records.
    • A paper copy and billing form is sent to the interpreting physician for interpretation. The physician provides the interpretation via the transcription and signs electronically. Physician includes the name of provider to cc interpretation to.
    • A copy is maintained in the pulmonary lab for 2 years.


Solomons. N.W. Evaluation of carbohydrate absorption: The Hydrogen Breath Test in Clinical Practice. Clinical Nutrition Journal 1984;3: 71-7 8.

Dipalma J.A. Narvaez R.M. Prediction of lactose malabsorption in referral patients. Digestive Diseases and Sciences 1988;33:303.

Fernandes J., Vos C.E. Douwes A.C., Slotema E. and Degenhart H.J. Respiratory hydrogen excretion as a parameter for lactose malabsorption in children. American Journal of Clinical Nutrition 1978;31: 597.

Recommended Dosages

Requesting physician can specify a lower dose.