Marilyn Ong¹, Neil A Chambers², Bruce Hullett³, Thomas O Erb⁴, Britta S Von Ungern-Sternberg⁵

¹Registrar, Department of Anaesthesia, Princess Margaret Hospital for Children, Subiaco WA 6008, Australia
²Head of Department, Department of Anaesthesia, Princess Margaret Hospital for Children, Subiaco WA 6008, Australia
³Consultant, Department of Anaesthesia, Princess Margaret Hospital for Children, Subiaco WA 6008, Australia
⁴Associate Professor, Division of Anaesthesia, University Hospital for Children, Basel, Switzerland
⁵Consultant, Department of Anaesthesia, Princess Margaret Hospital for Children, Subiaco WA 6008, Australia and Division of Clinical Sciences, Telethon Institute for Child Health Research, Roberts Road, Subiaco WA 6008 Australia

Introduction: Hyperinflation of laryngeal mask airway (LMATM) and tracheal tube cuffs can cause harm by exerting high pressures on pharyngolaryngeal structures thus impairing mucosal perfusion. In many institutions, cuff pressure monitoring is not routine and is replaced instead by the use of clinical endpoints. In a prospective audit, we assessed the usefulness of these common clinical endpoints in avoiding LMATM and tracheal tube cuff hyperinflation in children.

Methods: Following approval by the local Ethics Committee, we measured cuff pressures in 640 children at induction and immediately before emergence from anaesthesia using a calibrated cuff manometer (Portex Limited, Hythe, Kent, United Kingdom, range 0-120 cmH2O, pressures exceeding 120 cmH2O were set at 140 cmH2O for statistical purposes). According to the institution's routine management and in compliance with manufacturer's recommendations, the clinical endpoints were set as follows:
i) LMATM: Slight outward movement;
ii) Tracheal tube: Disappearance of an audible leak around the cuff during manual ventilation (Peak pressure 20 cmH2O).

Results: In the LMATM group (sizes 1-4), median cuff pressures were 90 to >120 cmH2O at induction and 105 to >120 cmH2O before emergence. The tracheal tube group (sizes 3-7) had median cuff pressures ranging from 40-60 cmH2O at induction, and 45-70 cmH2O at emergence. The use of nitrous oxide saw a consistent rise in cuff pressure between the first and second readings. This was not observed where nitrous oxide was not used.

Conclusion: Use of clinical endpoints alone was associated with significant hyperinflation of both the LMATM and tracheal tube cuffs in almost all patients. This is further exacerbated by nitrous oxide use. In order to avoid unnecessary hyperinflation in LMATM and tracheal tube cuffs, the routine use of cuff manometers is mandatory in children, particularly when using small sized airway devices.