Randomised comparison of a new paediatric laryngoscope with the Miller and Macintosh blades
Authors: Chawathe M.S. , Jones P.L. , Gildersleve C.D. , Jones R.M. , Armstrong S.H. , Aguilera I.M. 
Published: March 2003

Introduction  Traditionally in the United Kingdom, a straight laryngoscope blade such as Miller is used to intubate neonates and infants and a curved blade such as Macintosh is used for children above 1 year of age. The Cardiff paediatric laryngoscope blade was developed by combining elements of both curved and straight blade laryngoscopes with the aim of creating a universal blade that could be used to intubate children of all age groups. This would eliminate the problem of choice of blade for occasional users of paediatric laryngoscopes.

Method  With Ethics Committee approval and written informed parental consent, 40 patients < 1 year and 40 patients > 1 year of age needing intubation as part of their anaesthetic technique were recruited. In patients less than 1 year of age the Cardiff blade was compared with the Miller infant blade (Group 1). In patients over 1 year of age the Cardiff blade was compared with the Macintosh size 2 blade (Group 2). Following routine anaesthetic induction and institution of standard monitoring anaesthesia was maintained with 100% oxygen and sevotlurane prior to laryngoscopy. Laryngoscopy was performed by paediatric anaesthetic consultants with each of the two blades, the sequence of which was randomly allocated. Anaesthesia was maintained with 100% oxygen and sevoflurane via a facemask between each laryngoscopy ensuring oxygen saturation was ≥ 94%. The time taken for each laryngoscopy was recorded. This was the time taken from picking up the laryngoscope until the best view was obtained. For each blade the best obtainable view at laryngoscopy was recorded according to the modified Cormack and Lehane score (1). A maximum of 30 seconds was allowed for each laryngoscopy. If an adequate view was not obtained with the first Miller or Macintosh laryngoscope, then the anaesthetist was allowed to change to a more appropriate sized blade. If this occurred, the time quoted in the result is the time taken from picking up the final blade to the best view. The patient was intubated at the end of the second laryngoscopy and routine anaesthetic care continued. A P < 0.05 was significant.

Results  Time to obtain best view was significantly faster with the Cardiff blade in Group 1 but this difference was not seen in Group 2. There was no difference between blades for the best view obtained. In Group 1, 5% (2/40) cases using Miller blade needed to change from size 0 to size 1. One case was unintubatable with the Miller blade and a Cardiff blade had to be used. No cases using the Cardiff blade needed another blade to obtain best view. In Group 2, there was difficulty in obtaining view in two patients, [5%(2/40)], with both the Macintosh size 2 and Cardiff blades. In these two patients a size 3 Macintosh blade was used. Both patients were 14 years old.

Discussion and Conclusion  The Cardiff blade performed better than the Miller blade in Group 1 and equally as well as the Macintosh blade in Group 2. The Cardiff blade could be used as a universal alternative to conventional Miller and Macintosh blades in neonates and young children, thus reducing difficulties with choice of laryngoscope for infrequent paediatric intubators.