A comparative study of Gum elastic bougie preloaded over the guide rail of the C-MAC versus stylet for ease of intubation in patients under simulated cervical spine immobilisation: implications for emergency airway management

Technical Summary: Comparative Study of Gum Elastic Bougie vs. Stylet with C-MAC D-Blade in Simulated Cervical Spine Immobilisation

Problem Statement
In patients with suspected or confirmed cervical spine (C-spine) injuries, airway management is complicated by the necessity of maintaining manual in-line stabilisation (MILS). This immobilisation restricts neck extension and mouth opening, often resulting in a difficult glottic view (higher Cormack–Lehane grade) and increased risk of spinal movement during laryngoscopy. While video laryngoscopes (VL), specifically the C-MAC D-Blade with its 40° angulation, offer improved glottic visualization without requiring axis alignment, they present a specific challenge: the endotracheal tube (ETT) must be sharply angulated to navigate the blade's curve and pass through the vocal cords. Without an introducer, the ETT risks contacting the posterior laryngeal wall or arytenoids, leading to failed intubation. Although both stylets and gum elastic bougies (GEB) are used as introducers, the efficacy of preloading a GEB over the C-MAC guide rail versus using a standard 60° angulated stylet in the context of simulated C-spine injury had not been rigorously investigated in large-scale human clinical trials.

Methodology
The authors conducted a prospective, single-centre, randomised controlled trial (RCT) involving 52 adult patients (ASA PS I/II, aged 18–74) undergoing elective surgery under general anaesthesia. The study was registered with the Clinical Trials Registry–India and approved by the Institutional Ethics Committee.

• Intervention: Patients were randomised into two groups:
  • Group S (Stylet): The ETT was preloaded with a 60° angulated stylet (Karl Storz C-MAC GUIDE).
  • Group B (Bougie): A gum elastic bougie (Portex Tracheal Tube Introducer) was preloaded over the guide rail of the C-MAC D-Blade. The bougie was advanced into the trachea under vision, detached from the blade, and the ETT was railroaded over it.
• Simulation of Injury: Prior to laryngoscopy, MILS was applied to all participants to simulate C-spine immobilisation.
• Procedure: All intubations were performed by a single senior anaesthesiologist experienced with the C-MAC system.
• Outcome Measures:
  • Primary: Time taken for intubation (from blade insertion to capnograph trace appearance).
  • Secondary: Ease of intubation (4-point Likert scale), number of attempts, need for additional manoeuvres (e.g., external laryngeal manipulation, tube rotation), and complications (trauma, bleeding, desaturation).
• Statistical Analysis: A sample size of 52 (26 per group) was calculated to detect a clinically significant mean difference of 13.3 seconds with 95% power. Data were analysed using SPSS, employing t-tests for parametric continuous variables and chi-square tests for categorical variables.

Key Results

• Intubation Time: The Stylet group (Group S) demonstrated a statistically significant reduction in intubation time compared to the Bougie group (Group B).
  • Group S: 53.34 ± 19.86 seconds.
  • Group B: 72.27 ± 28.05 seconds.
  • p-value: 0.007.
• Ease of Intubation: There was no statistically significant difference in the ease of intubation between the two groups (p = 0.258).
  • Grade 1 (Easy, no manoeuvres): 69.2% in Group S vs. 50% in Group B.
  • Grade 2 (Difficult, manoeuvres needed): 30.8% in Group S vs. 50% in Group B.
  • No Grade 3 or 4 (failed) intubations occurred in either group.
• Attempts and Manoeuvres: All participants in both groups were successfully intubated on the first attempt. While 50% of Group B required additional manoeuvres compared to 30.8% of Group S, this difference was not statistically significant.
• Complications: Complications were minimal and comparable. 96.2% of Group S and 92.3% of Group B experienced no complications. Isolated cases of blood on the ETT or soft tissue trauma occurred in single participants in each group, with no statistical difference.

Significance and Claims
The study concludes that both the gum elastic bougie and the stylet are effective adjuncts for intubation with the C-MAC D-Blade in patients with simulated cervical spine injury. Both techniques yielded high first-attempt success rates and similar safety profiles regarding complications and the need for additional manoeuvres.

The authors claim that while the gum elastic bougie is a viable alternative for airway management in cervical spine injury patients, the stylet offers a distinct advantage in speed, reducing intubation time by approximately 19 seconds. The authors suggest that in emergency or trauma settings where rapid airway control is critical—particularly in high-risk patients prone to early desaturation (e.g., ICU, trauma, pregnancy)—the stylet may be preferable due to this time efficiency. However, they note that the absolute time difference (approx. 18 seconds) may not be clinically decisive in all scenarios, provided preoxygenation is adequate.

The paper emphasizes that these findings are derived from an elective surgical population with simulated immobilisation. Consequently, the authors modestly state that while the results can be extrapolated to emergency settings, further multicentre studies involving actual trauma patients and diverse, high-risk cohorts are necessary to fully validate generalizability and reduce selection bias.