New formulae for predicting tracheal tube length.

BACKGROUND: The aim of this study was to determine the accuracy of standard techniques for estimating oral and nasal tracheal tube length in children and to devise more accurate predictive formulae that can be used at the bedside.

METHODS: Data were collected from 255 children who required tracheal intubation whilst on the Pediatric Intensive Care Unit over a period of 1 year. Age, weight, the final length of the tracheal tube and the internal diameter were documented. Patients with a tracheostomy were excluded from the study.

RESULTS: Using linear regression the following formulae best predicted final tracheal tube length. For children over 1 year of age: Insertion depth (cm) for orotracheal intubation = age/2 + 13 Insertion depth (cm) for nasotracheal intubation = age/2 + 15 For children below 1 year of age: Insertion depth of orotracheal tube (cm) = weight/2 + 8 Insertion depth of nasotracheal tube (cm) = weight/2 + 9

CONCLUSIONS: Current Advanced Paediatric Life Support guidelines underestimate the appropriate tracheal tube lengths for orotracheal intubation in children over 1 year of age. Similarly, the novel weight-based formulae for tracheal tube lengths in children below the age of 1 year proved more accurate than standard reference charts. We therefore recommend that these new formulae are prospectively evaluated.