Progress report. Breath analysis tests in gastroenterology

Abstract

Analysis of certain constituents in breath exhaled after the administration of various substrates has been found to have potentially important applications, and interest in breath tests is increasing for a number of valid reasons. In some cases the gases measured are produced in chemical reactions that are difficult to quantitate in any other way, because they take place either inside cells or in the inacccessible regions of the gastrointestinal tract. Secondly, exhaled breath is easy to collect by simple, noninvasive, and esthetically acceptable means, often using disposable or cheap apparatus readily adapted to local hospital or even field conditions. Thirdly, serial studies can be performed to assess the course of a disease or its response to treatment without causing pain or hardship. Fourthly, the analysis of the breath specimens is simple, automated, and potentially highly cost effective. Fifthly, breath tests do not depend on good pulmonary function for their accuracy to the same degree that tests involving, for example, urine depend on accurate collections and on good renal function. This is because the gases being sought diffuse readily across biological membranes down concentration gradients, pass into plasma and thence into alveolar air. Admittedly, severe metabolic or respiratory acid base problems would interfere with a breath test, but in the presence of these abnormalities such tests probably would not be performed. Finally, breath tests are safe for use in adults and some of them are safe for use in children. In this report each of the exhaled gases of gastroenterological interest are considered and the present methods, applications, and areas of potential usefulness are reviewed.