Hyperangulated Video Laryngoscopes Used for Intubation With Simultaneous Cervical Spine Immobilization

This study will evaluate four videolaryngoscopes used for intubation of patients with cervical spine immobilization. Two hundred adult patients (females and males) with ASA (American Society of Anesthesiologist) status 1-3 will be scheduled for elective laparoscopic surgery at the Mazowiecki Szpital Specjalistyczny in Radom, Poland. Patients with known difficult laryngoscopy, difficult face mask ventilation, with previous history of awake tracheal intubation, those aged under 18 years or patients with BMI > 30 kg m-2 will be excluded from the study. All patients will receive oral premedication with 7.5 mg midazolam 30 minutes before the start of anaesthesia. A standard monitoring will be applied. This consists of ECG, NIBP (non-invasive blood pressure), SpO2, TOF (train-of-four) and volatile anaesthetic concentration. In order to achieve cervical spine immobilization, a Patriot® cervical collar (Össur hf., Reykjavik, Iceland) will be applied. The size of the collar will be adjusted to the patient's anatomy. Furthermore, the cervical collar will be fixed to allow a minimal mouth opening of 20 mm. All patients will be placed in a neutral position and will be pre-oxygenated with FiO2 1.0 for three minutes prior to induction. Anaesthesia will be induced with fentanyl (1-2 µg ml-1) and propofol (2-3 mg ml-1). Rocuronium (0.6 mg ml-1) will be used as a neuromuscular blocking agent. Adequate neuromuscular block will be confirmed and controlled throughout the procedure with TOF Watch (Organon, Dublin, Ireland). A cuffed, size 7.5 tracheal tube with stylet (Sumi, Sulejówek, Poland) will be used for intubation. A single-use hyperangulated blade will be used in all studied devices. Correct placement of the tracheal tube will be confirmed by videolaryngoscopy, capnography and chest auscultation. All patients will be anaesthetised by experienced consultant anaesthetists with over 10 years of clinical practice after completion of specialist training. Furthermore, all anaesthetists participating in the study will be trained beforehand with all VLs used until they feel competent. Only two intubation attempts with a studied videolaryngoscope will be allowed. A single attempt will be limited to 60 seconds. A failure is defined as an attempt which lasts more than 60 seconds, when saturation drops below 90%, after two unsuccessful attempts, when airway injury or bronchospasm occurrs. A single-digit number will be allocated to each of the studied videolaryngoscopes: 1 for the C-MAC PM, 2 for the McGrath, 3 for the VisionPro and 4 for the AceScope. A single sheet of paper containing printed number will be placed in an opaque envelope. Then they will be assigned to the participating anaesthetist by computer-generated randomization. The SPSS 29.0 software (IBM, Armonk, NY, USA) will be used for allocation. Furthermore, patients will be blinded to randomization.

The primary outcomes are the intubation time (Ti) and the first-attempt success. The Ti is defined as the time from picking up the videolaryngoscope until the correct placement of the tracheal tube will be confirmed by capnography. A stop watch of a mobile phone (Apple, Cupertino, CA, USA) will be used to measure Ti. The secondary outcomes include the ease-of-use and the time required to achieve the glottic view (Tg). The former will be evaluated using the NRS (Numerical Rating Scale). This is an eleven-point scale, i.e. from 0 to 10, and the score 0 denotes a very difficult and complicated to use device while 10 corresponds to an user-friendly equipment. The Tg is defined as the time from picking up the videolaryngoscope until the optimal entry-to-the-larynx view is achieved.

Collected data will be analysed using Statistica 14.0 (TIBCO Software, Palo Alto, CA, USA) and Microsoft Office Excel 2021 spreadsheet (Microsoft, Redmond, WA, USA). The Wilcoxon signed-rank test and the paired Student t-test will be used for data analysis. Continuous variables will be presented either as mean ± SD (standard deviation) or median (IQR - interquartile range) for non-normally distributed data. The Kolmogorov-Smirnov test will determine whether the analysed variables matches the characteristics of a normal distribution. We assume that the overall success rate of intubation in obese patients will be 90% (α = 0.05, 2-sided, β = 0.1, 95% CI). The calculated sample size requires 195 participants and the final adjusted sample size will be 200 patients to compensate for dropouts. A p-value of less than 0.05 (p < 0.05) is considered statistically significant.