Effect of meal size and test duration on gastric emptying and gastric myoelectrical activity as determined with simultaneous [13C]octanoate breath test and electrogastrography in normal subjects using a muffin meal.

Our purpose was to determine the effect of meal size on gastric emptying (GE) as measured by octanoate breath test (OBT), to determine the effect of the duration of breath collections on assessment of GE by OBT, and to determine the effect of meal size on gastric myoelectrical activity as measured by electrogastrography (EGG). Fourteen normal subjects underwent two modified [13C]OBTs using muffin meals of 250 or 350 kcal mixed with 100 mg [13C]sodium octanoate. T(1/2) for GE was determined for both the entire postprandial 6-hr breath collection and a truncated initial 4-hr data set. EGG was recorded for 30 min prior to the muffin meal and 4 hr postprandially. Using the 6-hr breath collection data, the T(1/2) was 177 +/- 7 (mean +/- SEM) for the 350-kcal meal compared to 153 +/- 7 min (P < 0.01) for the 250-kcal meal. Using the 4-hr data, the T(1/2) for the 350-kcal meal was 244 +/- 32 min compared to 165 +/- 12 min (P < 0.05) for the 250-kcal meal. The ratio of postprandial to fasting EGG power of the dominant frequency for the 350-kcal meal (1.9 +/- 0.4) was higher than that for the 250-kcal meal (1.3 +/- 0.6). T(1/2) for the 350-kcal meal using 4- and 6-hr data was significantly correlated with the 4-hr power ratio (r = 0.68 and 0.67; P < 0.05, respectively), but poorly correlated for the 250-kcal meal. In conclusions, GE and EGG are affected by meal size. Using the muffin-based [13C]OBT, T(1/2) for the 350-kcal meal was significantly longer than for a 250-kcal meal. Longer T(1/2) values were obtained with shorter breath sampling durations. The postprandial to fasting power ratio for the 350-kcal meal was greater than that for the 250-kcal meal.