Nitrous oxide: Effect on accumulation rate and uptake of bowel gases

Breathing 79% nitrous oxide (N ₂O) in oxygen increased the rate of accumulation of bowel gas during intraluminal bowel segment infusions of hydrogen, methane (CH ₄), air, or carbon dioxide (CO ₂) in 4 pentobarbital - anesthetized dogs more than did breathing 100% oxygen. A N ₂O-associated increase in the volume of naturally produced intestinal gas in 5 halothane-anesthetized ponies corroborated the findings in the dog studies. In a second group of 4 dogs, a bolus of CH ₄ or CO ₂ was injected into the bowel lumen. When the dogs breathed O ₂ the bowel gas volume decreased. Gas was virtually absent in the CO ₂-containing segment within 20 min. Breathing N ₂O increased the volume of the segments containing CH ₄ while the CO ₂ segments decreased less rapidly than during O ₂ breathing. Breathing O ₂ after 30 min of N ₂O breathing caused little change in the rate of decrease in CO ₂ segment volumes. However, the CH ₄ segment volume ceased to increase and eventually returned toward control volumes.