Gastric Emptying Breath Tests.pdf

REVIEW Retention, Fixation, and Loss of the [13C] Label: A Review for the Understanding of Gastric Emptying Breath Tests Masaki Sanaka ? Takatsugu Yamamoto ? Yasushi Kuyama Received: 7 June 2007 / Accepted: 27 October 2007 / Published online: 29 February 2008
Springer Science+Business Media, LLC 2008 Abstract A [13C]-breath test is a promising method for measuring gastric emptying. The methodological relevance is based on a close correspondence between gastric emp- tying of [13C]-acetate/octanoate (input) and pulmonary excretion of [13CO2] (output). Despite the close input- output correspondence, the pulmonary output is quite remote from the gastric input: the pulmonary output is delayed compared to the gastric input, and the total recovery of [13CO2] in the breath is incomplete. This review focuses on the kinetics of [13C]-acetate/octanoate in the body and suggests that (1) the delayed pulmonary output results from temporal retention of [13CO2] in the well-perfused tissues (heart, brain, etc.), (2) the incomplete recovery results from incorporation of the label into met- abolic products (ketone bodies, amino acids, etc.) or from fixation of [13CO2] in the low-perfused tissues (bone, skeletal muscle, etc.), and (3) knowledge on the retention is the key to appropriate interpretations of breath test results. Recognition of these kinetic aspects is essential for appropriate interpretations of these breath test results. Keywords Breath test
Gastric emptying
Fixation
Retention
Turnover Introduction Gamma scintigraphy is regarded as the reference method for measuring gastric emptying, but the technique has the critical drawback of substantial irradiation [1]. As a non- radioactive alternative, a breath test using a stable isotope ([13C]) is now widely used in research and clinical settings [2, 3]. In the breath tests, the [13C] label incorporated in a free fatty acid (acetic acid or octanoic acid) is used as a tracer. Labeled acetate and octanoate are applied to