Estimation of the correct length of tracheal tubes in adults

Estimation of the correct length of a tracheal tube is extremely important and should be tailored to the needs of the individual patient. One hundred and eight patients who required tracheal intubation during anaesthesia were studied. The predicted length was estimated in each patient before induction of anaesthesia. The upper end of the cuff was aligned externally with the cricoid cartilage, while the more proximal part of the tube lay alongside the neck to the angle of the mandible. The tube was then curved forwards towards the upper incisor teeth, and the length at the teeth or gums was noted. The anaesthetist, who was unaware of the predicted length, intubated the trachea after induction of anaesthesia. The length of tube inserted was standardised in relation to the vocal cords, and the actual length of tube inserted was recorded. The estimated length was within 1.0 cm and 1.5 cm of the actual length in 91% and 97% of patients respectively.