Appropriate depth of placement of oral endotracheal tube and its possible determinants in Indian adult patients

BACKGROUND: Optimal depth of endotracheal tube (ET) placement has been a serious concern because of the complications associated with its malposition. AIMS: To find the optimal depth of placement of oral ET in Indian adult patients and its possible determinants viz. height, weight, arm span and vertebral column length. SETTINGS AND DESIGN: This study was conducted in 200 ASA I and II patients requiring general anaesthesia and orotracheal intubation. METHODS: After placing the ET with the designated black mark at vocal cords, various airway distances were measured from the right angle of mouth using a fibre optic bronchoscope. STATISTICAL ANALYSIS: The power of the study is 0.9. Mean (SD) and median (range) of various parameters and Pearson correlation coefficient was calculated. RESULTS: The mean (SD) lip-carina distance, i.e., total airway length was 24.32 (1.81) cm and 21.62 (1.34) cm in males and females, respectively. With black mark of ET between vocal cords, the mean (SD) ET tip-carina distance of 3.69 (1.65) cm in males and 2.28 (1.55) cm females was found to be considerably less than the recommended safe distance. CONCLUSIONS: Fixing the tube at recommended 23 cm in males and 21 cm in females will lead to carinal stimulation or endobronchial placement in many Indian patients. The lip to carina distance best correlates with patient's height. Positioning the ET tip 4 cm above carina as recommended will result in placement of tube cuff inside cricoid ring with currently available tubes. Optimal depth of ET placement can be estimated by the formula “(Height in cm/7)-2.5.”