Ultrasound for Double Lumen Endotracheal Tube

The patients will be allocated to 2 groups: the ultrasound group and the clinical group. The correct position of the double lumen tube will be determined by ultrasound (Sonoscape S6®) for the patients of the one group (group U) and by clinical examination for the patients of the other group (group C). The correct placement will be verified by bronchoscopy (Pentax®). The two methods will be compared in terms of sensitivity and specificity. The main purpose of the study is to determine if the ultrasound can be used for determination of the correct placement of the left sided double lumen endotracheal tube