A 10-minute lecture will be delivered before the start of the study. It will explain how to use the studied devices. Following the lecture all participants will be able to familiarise themselves with the equipment and practice for 30 minutes. A skill station will be set up containing an intubation manikin AT Kelly Torso (Laerdal Medical AS, Stavanger, Norway). A reduced movement of the cervical spine will be achieved by application of a Patriot® cervical collar (Össur hf., Reykjavik, Iceland). After completion of the initial practice the intubation manikin with the cervical collar on will be placed on and secured to the driver's seat of a medium-sized passenger car (FIAT S.p.A., Turin, Italy). The car will then be positioned on its left side and secured in place by firemen from a local fire brigade. The access to the manikin will only be allowed from the front i.e. through the opening created after removal of the windscreen. A single digit number will be allocated to each of the four studied devices i.e. 1 for the SLIPA device, 2 for the I-gel, 3 for the LMA Supreme and 4 for the LTS. Each study participant will be asked to randomly give a number (either 1, 2, 3 or 4) and will then be given the corresponding airway device to use. The maximum number of insertion attempts will be limited to three per device. The time required to insert the device and achieve a successful ventilation (Tiv) will be recorded. It will be measured using a stopwatch of a mobile phone (Apple Inc., Cupertino, California, USA). Efficacy of insertion/ventilation and the ease of use by the operator will also be assessed. The latter will be measured using an 11-point numerical rating scale (NRS) where 0 corresponds to a very difficult to use device and 10 indicates an easy to use and user-friendly device. A manual resuscitator (Ambu A/S, Ballerup, Denmark) will be used for ventilation and will be readily available to the paramedics. The study participants will perform all insertions with each of the four supraglottic airway devices. A failed insertion and ventilation is defined as an attempt during which the manikin cannot be ventilated or an attempt that lasted longer than 120 seconds. Only those who failed to ventilate will be allowed another attempt. All the obtained data will be analysed using Microsoft Office Excel 2021 spreadsheet (Microsoft Corporation, Redmond, WA, USA). The Kolmogorov-Smirnov test is utilised to determine whether the analysed variables matched the characteristics of a normal distribution. A paired Student t-test and the Wilcoxon signed-rank test will be used for data analysis. Based on our previous unpublished pilot study and assuming that the overall success rate of intubation in patients with a difficult airway would be 90% (α =0.05, 2-sided, β =0.1), 46 participants will be required. The final adjusted sample size, allowing a drop-out rate of about 10%, is 50 and this is the final number of participants enrolled into the study. A p-value of less than 0.05 (p\<0.05) is considered statistically significant.
