Methodology of the H2 breath test. I. Collection and storage for gas measurement.

The measurement of hydrogen and methane in expired air is widely used in the field of gastrointestinal diagnosis. Techniques as simple and as reliable as possible are therefore requested for the collection and storage of breath samples. As far as collection is concerned, we compared three systems of end-expiratory sampling: a modified Haldane-Priestley tube, a Y-piece device fitted to a plastic syringe and a commercially available two-bag system. There was a significant correlation between the results obtained with all three systems, suggesting that all are sufficiently reliable. However, the two-bag system does not require particular training on behalf of the operator or particular cooperation from the patients and also makes it possible to take samples from more than one patient at the same time. For the storage of breath samples plastic syringes are the most commonly used device. Nonetheless, at room temperature there is a leakage of hydrogen equal to 9% after 24 hours, increasing to 29% after 5 days of storage. Refrigeration of the syringes at -20 degrees C prevents any loss in the first 48 hours and limits it to 5% after 5 days. The stability of the methane was higher than that of the hydrogen: after 5 days the loss is 4% at room temperature and 2% at -20 degrees C. For both gases the losses increase significantly at a temperature of 37 degrees C and are not affected by the initial concentration of the stored gas.(ABSTRACT TRUNCATED AT 250 WORDS)