Rosenstock 2012.

Methods	Multi‐centre RCT. Three university hospitals, Copenhagen, Denmark
Participants	93 adult elective participants with anticipated difficult laryngoscopy requiring GA and awake oral intubation. Scheduled for gynaecological, abdominal, urological and ENT procedures No obesity inclusion, but 46 participants with BMI > 30 kg/m2 presented as subgroup. Outcome data (ITT analysis) obtained in personal communication with study authors Inclusion criteria: age > 18 years; ASA I to III; simplified airway risk index (SARI) > =4. Exclusion criteria: mouth opening < 15 mm; poor dental status; surgeon request of nasal intubation; contraindication to transtracheal injection 9 of total 93 participants did not complete protocol; 7 transtracheal injection impossible & 2 lack of co‐operation. Unclear how many of these were obese Mean BMI (SD): FIS 36.7 (6.1); VLS 38.2 (5.3) Mean age (SD): FIS 59.5 years (8.9); VLS 65.0 years (11.2)
Interventions	26 obese participants randomly assigned to FIS. Scope make not given. Berman II intubation airway size 8 or 9 for women  size 9 or 10 for men Assistant performed jaw thrust to expand oropharyngeal space. TT model not given. Participant position left to discretion of intubator 20 obese participants randomly assigned to VLS (McGrath series 5). Sniffing position used. A stylet was used to bend the tip of the tube 80 to 100 degrees
Outcomes	Failed intubation: "in the case the first technique failed after three attempts, then optimal patient positioning was secured before an attempt at tracheal intubation with the alternative device" Hypoxia of < 90% oxygen saturation during intubation attempt Participant report of discomfort during awake intubation measured on VAS score 0 (none) to 10 (worst possible) on discharge from recovery Tooth damage and signs of soft tissue damage. Bleeding reported Number of attempts at intubation Total time for intubation (from advancement of FIS or VLS behind teeth until appearance of a capnography curve) Intubator's evaluation of ease of technique VAS 0 to 10 (presented as medians)
Details of anaesthetic induction and intubation	Awake intubation Participants given glycopyrrolate 4 to 5 mcg/kg after IV cannula placed Nasal catheter giving 2 to 4 litres O2 Continuous remifentanil infusion 0.1 to 0.15 mcg/kg/min with bolus dose of 0.75 mcg/kg as needed to keep participant sedation to Ramsay score of 2 to 4. Topical analgesia: lidocaine 10% to oropharynx 50 to 100 mg lidocaine given by transtracheal injection Sufficient analgesia given to avoid coughing and achieve acceptance of TT Make of TT used not standardized—size and make chosen before randomization
Training and seniority of intubator	Six investigators all “thoroughly trained in difficult airway management and also specifically experienced in using [both devices]"
Notes	Two McGrath VLSs were provided by SECMA (Skaevinge, Denmark) to two hospitals for the duration of the trial. Statement that authors had no conflicts of interest and were not provided with any funding from the manufacturers
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Variable block‐size randomization, computer‐generated random numbers. First block included 20 patients and second block 15 patients"
Allocation concealment (selection bias)	Low risk	"Number assignment kept in sealed envelopes" Personal communication from authors—also numbered and opaque
Blinding of participants and personnel (performance bias) Failed intubation, first success, ease of intubation and time for intubation	High risk	Participants, investigators and care providers knew allocation
Blinding of participants and personnel (performance bias) Hypoxia	Low risk	All participants given 2to 4 litres of oxygen
Blinding of participants and personnel (performance bias) Patient‐reported outcomes	High risk	Participants, investigators and care providers knew allocation
Blinding of outcome assessment (detection bias) Failed intubation, first success, ease of intubation and time for intubation.	High risk	Participants, investigators and care providers knew allocation
Blinding of outcome assessment (detection bias) Hypoxia	High risk	Participants, investigators and care providers knew allocation
Blinding of outcome assessment (detection bias) Patient‐reported outcomes	High risk	Participants, investigators and care providers knew allocation
Incomplete outcome data (attrition bias) All outcomes	Low risk	No apparent losses to follow‐up in obese participants. ITT analyses in personal correspondence from study author
Selective reporting (reporting bias)	Low risk	All outcomes prespecified in Methods are reported
Other bias	Low risk

ENT: ear, nose and throat; FIS: flexible intubation scope; ITT: intention‐to‐treat; IV: intravenous; NMB: neuromuscular blockade; NMBA: neuromuscular blocking agent; POD: postoperative day; SAD: supraglottic airway device; TT: tracheal tube; VAS: visual analogue scale; VLS: videolaryngoscope.