Double lumen tubes (DLTs) appear to be a favourable method for the airway management during one lung ventilation (OLV) in thoracic surgery. Most commonly left sided DLT is used for OLV due to the anatomical advantage of left bronchus over right bronchus. Despite of the above fact it has been found that left sided DLT get misplaced to right main bronchus in about 4.2 % cases, especially in females and short stature patients.

Traditionally, it is thought that left and right bronchi divide in the same plane from trachea so left sided DLT to be rotated 90 degrees anticlockwise after bronchial tip of DLT has crossed the vocal cord to position bronchial lumen to left main bronchus. However, this conventional approach has been questioned by recent studies which suggest that left bronchus divide at an angle more than 90 degree with more posterior inclination. One study based on ct scan analysis of tracheobronchial tree had suggested that 110 degree anticlockwise rotation instead of conventional 90 degree anticlockwise rotation of DLT, whereas another study has advocated individualised rotation of DLT.[ Nevertheless, dimensions of  tracheobronchial tree vary in different races the findings of above studies  may not be reciprocated in Indian population. Hence,we plan this study  to determine the angle of anticlockwise rotation of left sided DLT for its optimal placement in indian population.