Purpose To quantify and compare the peak force applied on the glottis during endotracheal intubation across five laryngoscopy techniques, two intubation conditions (standard and simulated laryngospasm), and two operator experience levels, and to assess the effects of stylet use and operator anthropometric characteristics on applied force.

Methods This prospective, manikin-based experimental study enrolled 50 operators (30 experienced, 20 less experienced). Each performed endotracheal intubation using five techniques: direct laryngoscopy and videolaryngoscopy with a Macintosh blade, each with and without stylet, and videolaryngoscopy with a hyperangulated blade with stylet. A calibrated force sensor positioned at the glottis measured peak forces during standard and simulated laryngospasm conditions. Non-parametric statistical methods were used (Mann-Whitney U, Wilcoxon signed-rank, Friedman tests); effect sizes are reported as rank-biserial correlations.

Results Across all techniques, median glottic forces ranged from 4.8 N (IQR: 3.3–6.5) for videolaryngoscopy without stylet to 11.1 N (IQR: 7.5–14.5) for direct laryngoscopy with stylet under standard conditions. No significant differences in applied force were observed between experienced and less experienced operators for any technique–condition combination (all adjusted p = 1.0; |r| ≤ 0.27). Stylet use significantly increased glottic force across all conditions and groups (median increases 3.4–7.3 N; all p < 0.001; rank-biserial r ≥ 0.75). Videolaryngoscopy with a Macintosh blade produced significantly lower forces than hyperangulated videolaryngoscopy under standard conditions (adjusted p = 0.049). Neither grip strength nor hand size correlated with applied force.

Conclusion Glottic force during endotracheal intubation is determined primarily by technique and stylet use, not operator experience or anthropometrics. Stylet use is the single largest modifiable contributor to glottic force. These findings have implications for device selection, clinical training, and strategies to minimize airway trauma during intubation.

IMPLICATION STATEMENT This manikin-based study quantifies glottic forces during endotracheal intubation across laryngoscopy techniques, stylet use, and operator experience levels, providing the first comprehensive characterization of right-hand forces transmitted through the tube. Stylet use consistently and substantially increases glottic force regardless of technique or operator experience, informing device selection and training strategies to minimize airway trauma.

Thomas Hemmerling and Pascal Laferriere-Langlois have ownership interest in Divocco AI.

This study has been funded by the Department of Anesthesiology and Pain Medicine, Hopital Maisonneuve-Rosemont, CIUSSS de l Est de l Ile de Montreal, Montreal, Quebec, Canada

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

This study was approved by our local ethics committee (Comite d ethique de la recherche du CIUSSS de l Est de l'Ile de Montreal, Montreal, Quebec, Canada) on December 10th 2025 (Project number: 2026-4206). All participants signed the informed consent form.

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I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

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All data produced in the present study are available upon reasonable request to the authors