Brain Damage Following Collapse of a Polyvinyl Tube: Elasticity and Permeability of the Cuff

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Abstract
A 13-year-old boy undergoing tympanoplasty lasting 3 1/2 hours developed serious airway obstruction at the end of surgery leading to permanent brain damage. It appeared that the no. 7 Portex "blue line" endotracheal tube had collapsed under the cuff. This was concluded because deflation of the cuff had promptly relieved the obstruction of the airway. Further support for this conclusion was the finding that shortly after extubation the inflation of 8 ml air caused the tube to collapse. Collapse of these tubes cannot normally be produced unless they have been made to collapse shortly before. Investigation of such tubes in vitro at 37 degrees C showed that overinflation of the cuff caused a symmetrical collapse of the tube wall along the x-ray opaque blue line. The collapse occurred with cuff pressures varying from 310 mmHg up to 460 mmHg for tubes from different batches. During anaesthesia with 66% nitrous oxide, this gas together with carbon dioxide were found to diffuse into the cuff at steady rates of 3.69 vol % and 0.36 vol % per hour, respectively. Corresponding increases in intracuff volumes were found. It is advised that disposable tubes should be carefully inspected before use and that endotracheal cuffs should be deflated periodically during anaesthesia to avoid excessive rise in cuff pressure.