Partial occlusion of the Bain circuit causes respiratory acidosis under general anesthesia

The Bain circuit is a modification of the Mapleson D ventilation system used in general anaesthesia in children and adults. It has several advantages over other systems as it is light in weight, convenient, and has no valves. But it contains the risk of undetected leak or occlusion, because of its construction with a small inner tube, which provides the patient with fresh gas, inside a larger corrugated tube. We report a partial occlusion in the T-piece of the Bain circuit, leading to high peak pressure and respiratory acidosis under controlled ventilation in a 15-year-old boy.