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Intubation biomechanics: laryngoscope force and cervical spine motion during intubation with Macintosh and Airtraq laryngoscopes.

ABSTRACT: Laryngoscopy and endotracheal intubation in the presence of cervical spine instability may put patients at risk of cervical cord injury. Nevertheless, the biomechanics of intubation (cervical spine motion as a function of applied force) have not been characterized. This study characterized and compared the relationship between laryngoscope force and cervical spine motion using two laryngoscopes hypothesized to differ in force.Fourteen adults undergoing elective surgery were intubated twice (Macintosh, Airtraq). During each intubation, laryngoscope force, cervical spine motion, and glottic view were recorded. Force and motion were referenced to a preintubation baseline (stage 1) and were characterized at three stages: stage 2 (laryngoscope introduction); stage 3 (best glottic view); and stage 4 (endotracheal tube in trachea).Maximal force and motion occurred at stage 3 and differed between the Macintosh and Airtraq: (1) force: 48.8 ± 15.8 versus 10.4 ± 2.8 N, respectively, P = 0.0001; (2) occiput-C5 extension: 29.5 ± 8.5 versus 19.1 ± 8.7 degrees, respectively, P = 0.0023. Between stages 2 and 3, the motion/force ratio differed between Macintosh and Airtraq: 0.5 ± 0.2 versus 2.0 ± 1.4 degrees/N, respectively; P = 0.0006.The relationship between laryngoscope force and cervical spine motion is: (1) nonlinear and (2) differs between laryngoscopes. Differences between laryngoscopes in motion/force relationships are likely due to: (1) laryngoscope-specific cervical extension needed for intubation, (2) laryngoscope-specific airway displacement/deformation needed for intubation, and (3) cervical spine and airway tissue viscoelastic properties. Cervical spine motion during endotracheal intubation is not directly proportional to force. Low-force laryngoscopes cannot be assumed to result in proportionally low cervical spine motion.

SUBMITTER: Hindman BJ

PROVIDER: S-EPMC4110170 | biostudies-literature | 2014 Aug

REPOSITORIES: biostudies-literature

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Intubation biomechanics: laryngoscope force and cervical spine motion during intubation with Macintosh and Airtraq laryngoscopes.

Hindman Bradley J BJ Santoni Brandon G BG Puttlitz Christian M CM From Robert P RP Todd Michael M MM

Anesthesiology 20140801 2

<h4>Introduction</h4>Laryngoscopy and endotracheal intubation in the presence of cervical spine instability may put patients at risk of cervical cord injury. Nevertheless, the biomechanics of intubation (cervical spine motion as a function of applied force) have not been characterized. This study characterized and compared the relationship between laryngoscope force and cervical spine motion using two laryngoscopes hypothesized to differ in force.<h4>Methods</h4>Fourteen adults undergoing electi ...[more]

PMID: 24739996

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Project description:BackgroundMaintaining cervical immobilization is essential during tracheal intubation in patients with unstable cervical spines. When using the Macintosh laryngoscope for intubation in patients with cervical immobilization, substantial neck extension is required for visualization of the glottis. However, the C-MAC D-Blade videolaryngoscope may require less neck extension due to its acute angulation. We hypothesized that C-MAC D-Blade videolaryngoscopic intubation would result in less cervical spine movement than Macintosh laryngoscopic intubation. We compared the effects of C-MAC D-Blade videolaryngoscopic intubation and Macintosh laryngoscopic intubation in terms of cervical spine motion during intubation in patients with simulated cervical immobilization.MethodsIn this randomized crossover study, the cervical spine angle was measured at the occiput-C1, C1-C2, and C2-C5 segments before and during tracheal intubation with either a C-MAC D-Blade videolaryngoscope or Macintosh laryngoscope in 20 patients, with application of a neck collar for simulated cervical immobilization. Cervical spine motion was defined as the change in angle measured before and during tracheal intubation.ResultsThe cervical spine motion at the occiput-C1 segment was measured at 12.1 ± 4.2° and 6.8 ± 5.0° during Macintosh laryngoscopic and C-MAC D-blade videolaryngoscopic intubation, respectively, corresponding to a 44% reduction in cervical spine motion when using the latter device (mean difference, - 5.3; 98.33% CI: - 8.8 to - 1.8; p = 0.001). However, there was no significant difference between the two intubation devices at the C1-C2 segment (- 0.6; 98.33% CI: - 3.4 to 2.2; p = 0.639) or C2-C5 segment (0.2; 98.33% CI: - 6.0 to 6.4; p = 0.929).ConclusionsThe C-MAC D-Blade videolaryngoscope causes less upper cervical spine motion than the Macintosh laryngoscope during tracheal intubation of patients with simulated cervical immobilization.Trial registrationThis study was registered at ClinicalTrials.gov on June 26, 2018 ( NCT03567902 ).

Project description:A variety of instruments are used to perform airway management by tracheal intubation. In this study, we compared the MacIntosh balde (MB) laryngoscope with the Bonfils intubation fibrescope as intubation techniques. The aim of this study was to identify the technique (MB or Bonfils) that would allow students in their last year of medical school to perform tracheal intubation faster and with a higher success probability. Data were collected from 150 participants using an airway simulator ['Laerdal Airway Management Trainer' (Laerdal Medical AS, Stavanger, Norway)]. The participants were randomly assigned to a sequence of techniques to use. Four consecutive intubation 'trials' were performed with each technique. These trials were evaluated for differences in the following categories: the 'time to successful ventilation', 'success probability' within 90 s,'time to visualisation' of the vocal cords (glottis), and 'quality of visualisation' according to the Cormack and Lehane score (C&L, grade 1-4). The primary endpoint was the 'time to successful ventilation'in the fourth and final trial.There was no statistically significant difference in the 'time to successful ventilation' between the two techniques in trial 4 ('time to successful ventilation': median: MB: 16 s, Bonfils: 14 s, p = 0.244). However, the 'success probability' within 90 s was higher when using a Macintosh blade than when using a Bonfils (95 vs. 87%). The glottis could be better visualised when using a Bonfils (C&L score of 1 (best view): MB: 41%, Bonfils: 93%), but visualisation was achieved more rapidly when using a Macintosh blade (median: 'time to visualisation': MB: 6 s, Bonfils: 8 s, p = 0.003).The time to ventilation using the MacIntosh blade and Bonfils mainly did to differ, however success probabilities and time to visualisation primary favoured the MacIntosh blade as intubation technique, although the Bonfils seem to have a steeper learning curve. The Bonfils is still a promising intubation technique and might be easier to learn as the MB, at least in a manikin.

Project description:The aim of the study was to test the hypothesis that the results obtained with three different types of video laryngoscopes (UESCOPE VL-400, I-View, Non-Channeled Aitraq) with and without an endotracheal stylet should be better than the results obtained with a Macintosh laryngoscope in a simulated out-of-hospital scenario by a person without clinical experience. Primary outcome measures were the time taken to successfully achieve tracheal intubation (TI). Secondary outcomes included the grade of glottic view (Cormack and Lehane grades 1-4), the incidence of successful TI, the number of audible dental clicks indicating potential dental damage, the level of effort required to perform TI, and the operator's comfort during the procedure. The time required to achieve tracheal intubation successfully was significantly longer with the Macintosh laryngoscope and Airtraq than with the other video laryngoscopes. The use of the stylet significantly reduced the time required for tracheal intubation with the Macintosh laryngoscope (21.8 sec. vs. 24.0 sec., p = 0.026), UESCOPE VL 400 (18.1 sec. vs. 23.4 sec., p = 0.013), and Airtraq (22.7 sec. vs. 34.5 sec., p < 0.001). There were no significant differences in intubation time when using the I-View with or without stylets. No differences were observed in the Cormack-Lehane grading. The success rate of intubation was 100% for the Macintosh and I-View laryngoscopes used with or without stylets and for the UESCOPE VL 400 and Airtraq laryngoscopes used with stylets. Without stylets, the success rate of intubation was 96.6% for the UESCOPE VL 400 and 86.6% for the Airtraq. There were no significant differences in the risk of dental damage between the Macintosh, UESCOPE VL 400, I-View, and Airtraq laryngoscopes, regardless of the use of stylets (without and with stylets). The use of stylets significantly reduced dental damage only for the Airtraq laryngoscope: 8 (26.6%) vs. 2 (6.6%). Statistically significant differences in perceived exertion were observed between the mentioned laryngoscopes, both with and without stylets. However, there were no differences in the comfort of use between the laryngoscopes, regardless of the use of stylets (without and with stylets. The use of stylets led to better comfort in the case of the Macintosh (2.5 vs. 3, p = 0.043) and UESCOPE VL 400 (2 vs. 3, p = 0.008) laryngoscopes. In our study, the I-View and UESCOPE VL-400 video laryngoscopes provided better intubation results than the Macintosh laryngoscope in terms of time needed to intubate, glottis visibility, and reduction in dental damage. The use of the stylet did not significantly improve the intubation results compared to the results obtained in direct laryngoscopy. Due to the small study group and the manikin model, additional studies should be performed on a larger study group.

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Intubation biomechanics: laryngoscope force and cervical spine motion during intubation with Macintosh and Airtraq laryngoscopes.

Publications

Intubation biomechanics: laryngoscope force and cervical spine motion during intubation with Macintosh and Airtraq laryngoscopes.

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