After informed consent, we will recruit 74 adult ASA Gr I-II patients who are scheduled for elective open thoracic surgery requiring double-lumen tube insertion for one-lung ventilation.

Pre-operative airway assessment and the Mallampati score, inter-incisor gap and thyromental distance will be documented.

Using computer-generated tables, patient will be randomized to anaesthesiologists ( predefined 4-5 anesthesiologists) experienced with McGrath in addition to standard blade.  Previous six successful intubations in patients with single lumen tube will be considered as the criteria to label the anaesthesiologist experienced with McGrath scope.

 The intubator will have to use either the standard MacIntosh scope (blade 3) or the McGrath videoscope, based on randomization which will be concealed using sealed opaque envelopes. It will be ensured at the being of the trial that each intubator does near equal intubation with each scope. Randomization, thus,  will be done at two levels , intubator and scope.   

After attaching appropriate monitors and checklist, the patients’ lungs will be pre-oxygenated with 100% oxygen at a fresh gas flow of 6 litres/min for 3 minutes via a closely applied facemask. General anaesthesia will then be administered with intravenous fentanyl 2 microgram/kg followed by intravenous propofol 2-3 mg/kg or any other suitable induction agent.  After loss of consciousness, Injection rocuronium 1 mg/kg or other suitable relaxant will be administered and manual bag  â„ mask ventilation will be continued for 3 min. The appropriate double-lumen tube (size and side) will be inserted as clinically indicated. The tube will be lubricated well. The anaesthetist will insert the McGrath blade along the midline of the tongue as per standard recommendations. Once the glottis is seen clearly on the screen, a double lumen tube will be inserted into the patient’s mouth from the right side. When the distal tip of the tube will be seen to enter the trachea between the vocal cords, the stylet will be removed and the tube will be rotated 90 degrees under observation on the videoscope screen, either clockwise or anti-clockwise depending on the type of tube. The double-lumen tube will then be advanced and the blade removed from the patient’s mouth. Using the Macintosh laryngoscope blade, the tube will be inserted in the traditional fashion. Immediately after successful intubation, an assistant will inflate both cuffs with air and mechanical ventilation will commence. Correct positioning of the double-lumen tube will be determined clinically by auscultation of both lungs before and after selective clamping of the tracheal and bronchial lumens, and with a fibre optic bronchoscope to be inserted with the patient in the supine position.

Time taken for visualization of cord, defined as time from advancement of scope from dental arches to visualization of the glottis and the total time to intubate, defined as time from advancement of scope from dental arches to deflection of capnograph for each laryngoscope will be recorded.

A failed intubation is defined when the user cannot intubate the patient’s trachea after two attempts, each attempt being defined as not more than 120 seconds or fall of saturation to 90% whichever is earliest. A total of two attempts will be allowed to each performer. In between each attempt patient will be masked ventilated.

In case of failure to intubate after two attempts, with McGrath scope, intubation can be tried with standard MacIntosh blade. Any difficulty at intubation or mask ventilation at any point of time, the airway will be managed as per ASA difficult airway guidelines.

In such cases, the time to intubate will be taken as the addition of duration of each intubation attempt. However, cases in which intubation has failed twice, the time to intubate will not be considered in the analysis with respect to intubation time. The event will be recorded as a failure.

The performers are permitted to use external laryngeal pressure to improve the glottic view or to facilitate tube insertion. This would be recorded in the case form as an optimization manoeuvre.

However in case if the attempt has to be abandoned in view of an inappropriately sized DLT, the event will be recorded but the attempt and time will not be considered in the TTI for that patient.

In case of a mechanical damage to tube like tears of the tracheal or bronchial cuff, then a new double lumen tube will be inserted, and it will be recorded as a complication.

Once tube is in place, the placement of the tube will be confirmed and any alteration needed will be noted.

The injury i.e. visible trauma to lip or oral mucosa, presence of blood on laryngoscope blade will be recorded as minor injury. While, any bleeding requiring intervention in the form of packing or suturing or dental extraction of a previous normal tooth will be graded as major injury

Once tracheal intubation is accomplished successfully, the performer will score the glottic view as per Cornmack and Lehane grading and also score the ease of use of the laryngoscope on a numerical rating scale (NRS) (ranging from 1 for extremely easy to 10 for extremely difficult).

 The lowest value of arterial oxygen saturation, pre-intubation and  post-intubation blood pressure readings will be noted at 1,2,5 min

Presence of bronchospasm( wheeze on auscultation) will be noted.

Following surgery, the patient will be evaluated in the post anesthesia care unit for symptoms of sore throat and hoarseness on a scale of 0 (no hoarseness) - 10 (significant hoarseness). For analysis, the score will be clubbed as 0- nil, 1-3 mild, 4-6=moderate, 7-10= severe