Final answer:
A double lumen ETT is used for one-lung ventilation during surgery.
Step-by-step explanation:
A double lumen ETT, or endotracheal tube, is used for one-lung ventilation during surgery. It is a specialized tube that allows the anesthesiologist to separately ventilate each lung during certain surgical procedures. The tube has two separate channels: one for delivering oxygen and anesthesia gases to the lung being ventilated, and another for allowing exhaled gases to escape. By using a double lumen ETT, the surgeon can have better visual access to the surgical site and the anesthesiologist can ensure proper ventilation of both lungs during surgery.