Rebreathing of carbon dioxide caused by incompetent 'cage and disc' unidirectional valves has been reported earlier. Some manufacturers have changed the design of unidirectional valves to 'flexible leaflets'. We report a series of cases where a deformed membrane leaflet in expiratory unidirectional valves led to rebreathing of carbon dioxide.
Keywords: Anesthesia machine; circle breathing system; incompetent unidirectional valves.