Disconnect alarm failure in detection of common gas outlet disconnection

This laboratory study was prompted by two paediatric cases where low pressu re alarms and capnography failed to detect common gas outlet disconnection when using a T-piece pump ventilator: A carbon dioxide producing model lung was ventilated using the Glare ventil ator (a T-piece pump type ventilator;) via an Ayres T-piece. The T-piece us ed has 3 mm diameter fresh gas tubing Common gas outlet disconnects were ca rried out using varying fresh gas flows and ventilatory patterns. At fresh gas flows of less than 8 l/min, the low pressure alarm of the Glar e ventilator failed to sound following common gas outlet disconnection. Oxy graphy showed a rapid rise in inspired oxygen. End-tidal CO2 rose, whilst i nspired CO2 remained at zero, This experiment demonstrates that the Glare ventilator's low pressure alarm detects common gas outlet disconnection poorly when used with an Ayres T-p iece with narrow fresh gas tubing. Graphical representation of airway oxyge n content has merit as an aler-ting monitor for common gas outlet disconnec tion.