Carbon dioxide rebreathing caused by deformed silicon leaflet in the expiratory unidirectional valve
A nine-year-old boy was scheduled for the release of a burn contracture in the leg. Anesthesia was induced with propofol and a size 2.5 laryngeal mask airway (LMA) was inserted. Anesthesia was maintained with isoflurane using a circle breathing system, with the patient breathing spontaneously. The capnogram showed a progressive increase in EtCO2 with elevated FiCO2 (up to 8 mmHg), not altered by increasing the flow of fresh gas. Soda lime appeared unaltered. When ventilation was assisted manually, EtCO2 decreased to normal levels and touched baseline during inspiration. The problem recurred whenever the child was allowed to breathe spontaneously without assistance. Anesthesia was continued with assisted ventilation and further management was uneventful. On close inspection, the flexible leaflet of the expiratory UDV appeared minimally deformed. After the end of the procedure, the UDV was tested and found to be incompetent.