Effects of smoking on interdigestive gastrointestinal motility

The effect of smoking on interdigestive gastrointestinal motility is little studied but may play a role in gastrointestinal morbidity. We studied gastroduodenal motility in 10 volunteers (five smokers and five nonsmokers) using a water-perfused pressure catheter. A pH probe was placed in the duodenal bulb. Baseline motility was recorded until phase III of the migrating-motor complex had occurred in the stomach three times in order to record two complete cycles of MMC activity. Subjects then began smoking until phase III activity occurred again (mean duration of smoking 117 min). During the control period, all subjects had normal MMC cycles and there were no differences between smokers and nonsmokers. While smoking, no gastric phase III was observed in any subject and gastric motility was markedly reduced. In seven of 10 subjects, smoking did not prevent the occurrence of normal duodenal phase III activity. Three subjects had no duodenal phase III activity during smoking. The duodenal pH profile did not change during smoking and motilin levels continued to fluctuate in conjunction with phase III activity. In conclusion, smoking abolished phase III activity in the stomach without affecting the plasma motilin cyclic fluctuations or duodenal bulb pH. In contrast, smoking has little effect on duodenal motility.