Effect of various test meals on gastric and jejunal carbon dioxide: A study in healthy subjects

Objective. The normal pattern of carbon dioxide (CO₂) levels in the human stomach and small bowel after meals is unknown. The intraluminal carbon dioxide level is a sensitive and early marker for organ mucosal ischemia. CO₂ levels in both the stomach and small bowel are influenced by multiple factors other than adequacy of perfusion. Gastric acid production, salivary bicarbonate and CO₂ produced or absorbed by meals are the disturbing variables. Prolonged gastric (and jejunal) tonometry after meals can be of additional value in the work-up of patients suspected of (chronic) gastrointestinal ischemia. The purpose of this study was to challenge these problems using in vitro tested meals and a rigid acid-suppression regimen in a group of healthy subjects. Material and methods. Standard meals were tested in vitro on the ability to produce and buffer CO₂. Meals with the least CO₂ variations were subsequently used in healthy subjects. Tonometry of the stomach and jejunum was performed for 24 h, with optimal and controlled acid suppression. Results. Ten subjects were enrolled in the study. Acid production was sufficiently suppressed. The gastric PCO₂ baseline (fasting) was 6.5 (1.0), and significantly lower than the jejunum PCO ₂ baseline of 7.6 (0.9) kPa. The gastric baseline during the day was 6.9 (1.6), and significantly lower than the gastric baseline during the night of 8.0 (1.8), suggesting a diurnal variation of PCO₂. Increases in PCO₂ levels were seen in all subjects, after meals and between meals. Conclusions. Prolonged gastric and jejunal tonometry is feasible in humans. PCO₂ levels were seen to peak after, but also in-between, most meals. The diurnal variation in PCO₂ might reflect reversible gastric mucosal ischemia.