Abstract
This laboratory study was prompted by two paediatric cases where low pressure 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 Clare ventilator (a T-piece pump type ventilator) via an Ayres T-piece. The T-piece used has 3 mm diameter fresh gas tubing. Common gas outlet disconnects were carried 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 Clare ventilator failed to sound following common gas outlet disconnection. Oxygraphy showed a rapid rise in inspired oxygen. End-tidal CG2 rose, whilst inspired CO2 remained at zero.
This experiment demonstrates that the Clare ventilator's low pressure alarm detects common gas outlet disconnection poorly when used with an Ayres T-piece with narrow fresh gas tubing. Graphical representation of airway oxygen content has merit as an alerting monitor for common gas outlet disconnection.