H 2-breath testing for evaluation of oro-caecal transit time

The appearance in the expiratory breath of gases produced by colonic ferementation of an ingested organic compound may be used to measure oro-caecal transit. Both a liquid meal containing lactulose or a solid meal containing backed beans can be used in the assessment of oro-caecal transit. Ingestion of a meal is followed by a biphasic breath hydrogen profile in most subjects. The initial peak of hydrogen closely follows the meal whereas the second peak, associated with the head of the meal entering the caecum often occurs hours later. The H ₂ breath test is safe and usually well tolerated. However, the wide variation in the measurement of oro-caecal transit in normal subjects and the poor reproducibility ofthe test, in particular with the liquid meal, have limited its applications to the clinical. The test performance is better when applied to clinical pharmacology studies and it has been used to demonstrate the drug effects on oro-caecal transit.