The carbon dioxide production rate assumption biases gastric emptying parameters in healthy adults

Authors

  • Oonagh Markey,

    1. Hugh Sinclair Unit of Human Nutrition and Institute for Cardiovascular and Metabolic Research (ICMR), Department of Food and Nutritional Sciences, University of Reading, Reading, UK
    2. Department of Physical Education and Sport Sciences, University of Limerick, Limerick, Ireland
    Search for more papers by this author
  • Amir Shafat

    Corresponding author
    1. Physiology, School of Medicine, National University of Ireland, Galway, Ireland
    • Department of Physical Education and Sport Sciences, University of Limerick, Limerick, Ireland
    Search for more papers by this author

A. Shafat, Physiology, School of Medicine, National University of Ireland, Galway, University Road, Ireland.

E-mail: amir.shafat@nuigalway.ie

Abstract

RATIONALE

An altered gastric emptying (GE) rate has been implicated in the aetiology of obesity. The 13C-octanoic acid breath test (OBT) is frequently used to measure GE, and the cumulative percentage of 13C recovered (cPDR) is a common outcome measure. However, true cPDR in breath is dependent on accurate measurement of carbon dioxide production rate (math formula). The current study aimed to quantify differences in the 13C OBT results obtained using directly measured math formula (math formula) compared with (i) predicted from resting math formula (math formula) and (ii) predicted from body surface area math formula (math formula).

METHODS

The GE rate of a high-fat test meal was assessed in 27 lean subjects using the OBT. Breath samples were gathered during the fasted state and at regular intervals throughout the 6-h postprandial period for determination of 13C-isotopic enrichment by continuous-flow isotope-ratio mass spectrometry. The math formula was measured directly from exhaled air samples and the PDR calculated by three methods. The bias and the limits of agreement were calculated using Bland-Altman plots.

RESULTS

Compared with the math formula, the cPDR was underestimated by math formula (4.8%; p = 0.0001) and math formula (2.7%; p = 0.02). The GE Thalf was underestimated by math formula (13 min; p = 0.0001) and math formula (10 min; p = 0.01), compared with math formula.

CONCLUSIONS

The findings highlight the importance of directly measuring math formula production rates throughout the 13C OBT and could partly explain the conflicting evidence regarding the effect of obesity on GE rates. Copyright © 2013 John Wiley & Sons, Ltd.

Ancillary