Tracheal intubation (TI) is one of the fundamental and most recognized techniques in Anesthesiology, also essential in all units treating urgent pathology and critical patients. It involves advancing a tube through the vocal cords into the trachea to ventilate the patient. In thoracic surgery, it is often necessary to achieve lung isolation, ventilating only one lung while the operated lung remains collapsed and immobile. To achieve this, it is common to intubate the patient with a special tube: a double-lumen tube (DLT), larger than usual because it provides two ventilation channels, one for each lung.

Tracheal intubation with a DLT presents some peculiarities: its larger size and stiffness make manipulation and orientation in the oropharynx difficult. It has a curve at its distal end (the bronchial lumen) designed to slide into the left or right main bronchus as needed. The fact that the DLT passes between the vocal cords does not ensure its proper placement and function. Therefore, DLT intubation requires practice and experience, both to slide it between the vocal cords and to position it properly.

The classic technique for DLT intubation is "Direct Laryngoscopy" (DL). A traditional laryngoscope with a Macintosh blade is used to move the upper airway structures aside to allow direct visualization of the glottis. In recent years, to facilitate tracheal intubation, different videolaryngoscopes have appeared. A videolaryngoscope is a device similar to a traditional laryngoscope that allows, thanks to an image sensor located at its end, indirect visualization of the glottis on an integrated or external screen.

There is strong evidence for the benefit of using a VL over traditional DL in single-tube intubation in adult patients. However, although the use of VL for DLT intubation is becoming more common, there are few studies with small sample sizes comparing VL to DL for DLT intubation, so the evidence of its advantages or disadvantages is of low quality. It could improve glottic exposure and the percentage of success on the first attempt, although there is a possibility of increased tube malposition incidence and delayed intubation.

Therefore, Investigators propose a prospective, multicenter, randomized study comparing the traditional Macintosh blade laryngoscope (direct laryngoscopy) with the videolaryngoscope to facilitate orotracheal intubation with double-lumen tube in patients scheduled for thoracic surgery requiring lung isolation.

The purpose of this prospective multicenter randomized study is to compare successful intubation on the first attempt with the Macintosh laryngoscope vs the videolaryngoscope for double-lumen tube tracheal intubation in thoracic surgery. Investigators hypothesize that tracheal intubation using the videolaryngoscope will improve the frequency of successful intubation on the first attempt.

Inclusion Criteria:

• Age 18 years or older.
• Patients admitted to any of the participating hospitals in the study who are undergoing thoracic surgery.
• Need for intubation with a double-lumen tube.

Exclusion Criteria:

• Pregnant or lactating women.
• Individuals who do not have the capacity to understand their participation in the study.
• Need for tracheal intubation with a device other than videolaryngoscopy or direct laryngoscopy (fiberoptic bronchoscope, tracheostomy...).