This was a prospective, randomized, controlled, and cross-over study comparing two methods of cricothyrotomy in an obese surgical airway manikin. The study was performed in Gazi University Hospital, Ankara, Türkiye after approval by the Gazi University Ethics Committee (Date: 21.03.2023, Number: E.615448).

The study included emergency medicine residents at a university hospital. Emergency medicine residents who did not want to participate in the study, were not actively working at the time of the study and had previously performed a surgical airway were excluded.

Our two-sided hypothesis is that there is a difference in the first-attempt success rates of surgical airway techniques. Alpha was accepted as 0.05, and power as 80%. The ratio of the two groups was 1. A difference of 35% between the two groups was accepted as significant [11]. The sample size was calculated as 24 using G*Power version 3.1.9.4.

Before the start of the study, the residents received 45 min of didactic training in surgical airway management. Traditional surgical cricothyrotomy and bougie-guided cricothyrotomy techniques were demonstrated on a manikin by an emergency medicine specialist experienced in surgical airway and working as an instructor. The steps and materials used for both methods are shown in Tables 1 and 2.

The 3D-printed surgical airway manikin was obtained from the drawing at www.thingverse.com (Fig. 1). To form the cricothyroid membrane, 5 × 5 × 0.1 cm electrical tape was used. Then, to make the cricothyroid membrane impalpable, layers of 22-density 10 × 10 × 3 cm sponge, 10 × 10 × 2 cm visco sponge, diluted artificial blood in 2 × 2 inch bags, and 20 × 15 × 0.1 cm adhesive foam paper were formed on the manikin from bottom to top (Figs. 2 and 3). When the layers were assembled and fixed on the manikin, a thickness of 4 cm was reached between the skin and the cricothyroid membrane.

3D printed manikin created with cricothyroid membrane with electrical tape

Layers consisting of 22-density 10 × 10 × 3 cm sponge, 10 × 10 × 2 cm visco sponge, diluted artificial blood in 2 × 2 inch bags, and 20 × 15 × 0.1 cm adhesive foam paper from bottom to top to create an obese manikin

3D printed manikin with layers for obese simulation

After the 3D-printed manikin was made suitable for obese surgical airway simulation, it was placed on the stretcher and secured. The techniques were written on two different pieces of paper and placed in envelopes for randomization. The resident performing the procedure determined the first technique by selecting an envelope. Each resident performed both techniques. After completing the first technique, the resident performed the other technique. Each technique was given 180 s of procedure time for one attempt. Three attempts were allowed for each technique. Before the procedure, the participants were given five minutes to familiarize themselves with the manikin. The procedures began when the resident said, “I am ready.” During the procedures, a number 5 cuff tracheostomy tube was used for the traditional surgical cricothyrotomy, and a 6.0 cuff endotracheal tube was used for the bougie-guided cricothyrotomy. The procedure was considered successful if the balloon representing the manikin’s lung was inflated during artificial manual (Ambu) bag ventilation. If the procedure took longer than 180 s, it was stopped, and the next attempt was started. The procedure was considered unsuccessful if all three attempts for a technique failed.

The procedures were supervised and analyzed by two researchers. Age, gender, seniority, first method, procedure times for both methods, number of attempts, and success rate of the participants were recorded. During the procedure, the total procedure time from the time the practitioner said, “I’m ready” until the manikin was ventilated with an ambu bag was recorded with a chronometer.

At the end of the procedure, the participants were asked to rate both methods on a scale of 0–100 in terms of difficulty. A score of 0 was considered no difficulty, and 100 was considered extremely difficult.

The statistical analysis was performed using SPSS version 22 (SPSS Inc., Chicago, IL, USA). Frequency, mean, and standard deviation values were reported for the data. Normality was tested with the Shapiro–Wilk test. Categorical variables were statistically analyzed using Pearson’s chi-square and Fisher’s exact tests. Comparisons of numerical variables between two independent groups were analyzed using the Student’s t-test, as the normal distribution condition was met. A p-value of less than 0.05 was considered statistically significant.