Effect of meal and intravenous erythromycin on manometric and electrogastrographic measurements of gastric motor and electrical activity.

Electrogastrography (EGG) measures, on the skin surface, the myoelectrical activity attributable to gastric smooth muscle cells. The physiological significance of signal amplitude and variation has not been clearly established. The increased signal amplitude after eating a meal may be related to increased contractile activity or to gastric distension. This study investigates the effect of increased gastric motor activity, unaccompanied by gastric distension, on the EGG recording and compares it to the effect of a meal. Nine children (3 months to 15 years old), were assessed by antroduodenal manometry for chronic intestinal pseudoobstruction (N = 5), chronic vomiting (N = 2), and abdominal distension (N = 2). Synchronized EGG recording was performed simultaneously. During the study, four children were given a meal and five were given intravenous erythromycin 3 mg/kg over 1 hr. The ratio of the antral motor index (MI = number of waves x sum of amplitudes) determined 1 hr before a meal (or erythromycin) to that determined 1 hr after a meal (or during intravenous erythromycin) was calculated. The ratio of the running total spectrum power of the electrical signal at the same times was also calculated. Antral MI increased after a meal [MI ratio (mean +/- SE) 5.33 +/- 2.2] and after intravenous erythromycin (MI ratio: 9.36 +/- 2.6). The amplitude of the electrical activity also increased after the meal [power ratio (mean +/- SE) 3.01 +/- 0.65] and after intravenous erythromycin (power ratio: 1.23 +/- 0.39), but the increase was greater after the meal (P < 0.05 vs intravenous erythromycin). No correlation was found between antral MI ratio and running total spectrum power ratio. In conclusion, the increased amplitude of the gastric electrical activity recorded by the EGG after a meal seems to be only partly due to the increase in antral motor activity. The increase in power is also related to gastric distension.