The relationship between a person's height and appropriate endotracheal tube length

The relationship between a person's height and the dimensions of that person's upper airways has been studied in adult subjects. Using this relationship, formulae have been derived which predict appropriate lengths for endotracheal tubes. The formulae are as follows: 1. Orotracheal tube (teeth to mid-point of trachea) = Subject height (cm)/10 + 2 2. Orotracheal tube (teeth to mid-point of trachea + 3 cm) = Subject height (cm)/10 + 5 3. Nasotracheal tube (external naris to mid-point of trachea) = Subject height (cm)/10 + 8 These formulae are not foolproof but provide a useful working guide. All usual comfirmatory tests of correct placement should be employed.