The use of a height-based formula to predict the insertion depth of left-sided double-lumen tubes in thoracic surgery is now well established. The investigators have developed a formula to be used and published recently. The investigators verified the formula with the use of FOB. This observational study will use FOB checking if needed.~Our hypothesis is that DLT can insert without the use of FOB in most of the cases. That doesn't mean FOB is less required.
The use of height based formula to predict insertion depth of left-sided double lumen tube in thoracic surgery is now well established. The investigators have developed a formula to be used and published recently. The investigators verified the formula with the use of FOB. This observational study we are going to use with FOB checking if needed.