Comparison of intubation success and glottic visualization using King Vision and C-MAC videolaryngoscopes in patients with cervical spine injuries with cervical immobilization: A randomized clinical trial
- Department of Anaesthesiology and Critical Care, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Pondicherry, India
Prasanna U. Bidkar
Department of Anaesthesiology and Critical Care, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Pondicherry, India
DOI:10.4103/2152-7806.199560Copyright: © 2017 Surgical Neurology International This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.
How to cite this article: Dhanyasi Shravanalakshmi, Prasanna U. Bidkar, K. Narmadalakshmi, Suman Lata, Sandeep K. Mishra, S. Adinarayanan. Comparison of intubation success and glottic visualization using King Vision and C-MAC videolaryngoscopes in patients with cervical spine injuries with cervical immobilization: A randomized clinical trial. 06-Feb-2017;8:19
How to cite this URL: Dhanyasi Shravanalakshmi, Prasanna U. Bidkar, K. Narmadalakshmi, Suman Lata, Sandeep K. Mishra, S. Adinarayanan. Comparison of intubation success and glottic visualization using King Vision and C-MAC videolaryngoscopes in patients with cervical spine injuries with cervical immobilization: A randomized clinical trial. 06-Feb-2017;8:19. Available from: http://surgicalneurologyint.com/surgicalint_articles/comparison-of-intubation-success-and-glottic-visualization-using-king-vision-and-c%e2%80%91mac-videolaryngoscopes-in-patients-with-cervical-spine-injuries-with-cervical-immobilization-a-randomized-cl/
Background:Glottic visualization can be difficult with cervical immobilization in patients with cervical spine injury. Indirect laryngoscopes may provide better glottic visualization in these groups of patients. Hence, we compared King Vision videolaryngoscope, C-MAC videolaryngoscope for endotracheal intubation in patients with proven/suspected cervical spine injury.
Methods:After standard induction of anesthesia, 135 patients were randomized into three groups: group C (conventional C-MAC videolaryngoscope), group K (King Vision videolaryngoscope), and group D (D blade C-MAC videolaryngoscope). Cervical immobilization was maintained with Manual in line stabilization with anterior part of cervical collar removed. First pass intubation success, time for intubation, and glottic visualization (Cormack – Lehane grade and percentage of glottic opening) were noted. Intubation difficulty score (IDS) was used for grading difficulty of intubation. Five-point Likert scale was used for ease of insertion of laryngoscope.
Results:First attempt success rate were 100% (45/45), 93.3% (42/45), and 95.6% (43/45) in patients using conventional C-MAC, King Vision, and D blade C-MAC videolaryngoscopes, respectively. Time for intubation in seconds was significantly faster with conventional C-MAC videolaryngoscope (23.3 ± 4.7) compared to D blade C-MAC videolaryngoscope (26.7 ± 7.1), whereas conventional C-MAC and King Vision were comparable (24.9 ± 7.2). Good grade glottic visualization was obtained with all the three videolaryngoscopes.
Conclusion:All the videolaryngoscopes provided good glottic visualization and first attempt success rate. Conventional C-MAC insertion was significantly easier. We conclude that all the three videolaryngoscopes can be used effectively in patients with cervical spine injury.
Keywords: Cervical spine immobilization, glottic visualization, videolaryngoscopes
Although direct laryngoscopy has been used with variable success, it has the potential to cause greater cervical spine movement.[
The C-MAC (Karl Storz, Tuttlingen, Germany) is a portable videolaryngoscope, which has similar curvature as standard Mac Intosh (C blade) and a more angulated D blade. The King Vision Videolaryngoscope (KVVL) (King Systems, Noblesville, IN, USA) is one of the new indirect laryngoscope with channeled and nonchanneled blades. KVVL has a unique design, and high quality image can prove useful in cervical spine injury patients without movement of the neck. This study compared the C-MAC (both conventional and D blade) and KVVL in patients with proven/suspected cervical spine injury on cervical immobilization in terms of first attempt intubation success, laryngoscopic view, and time for intubation.
Approval for the study was obtained form the Institute ethics committee (project no: JIP/IEC/2014/8/365 (CTRI/2015/06/005936); and all patients signed an informed written consent. The study included adults, aged 18–60 years, with 1–2 grade American Society of Anesthesiologists (ASA) physical status and proven or suspected cervical spine injury. All were placed in cervical spine immobilization/rigid cervical collars, and scheduled for elective surgery to be performed under general anesthesia. A total of 135 patients were randomized into 3 groups (45 each): Group K (nonchanneled blade of King Vision), group C (conventional blade of C-MAC), and group D (D blade of C-MAC) was used for endotracheal intubation.
Pre-oxygenation with 100% O2 for 3 min was done with rigid cervical collar in place. All the patients were induced with 2 µg/kg of Fentanyl, 2 mg/kg of Propofol, and muscle relaxation was achieved with 0.1 mg/kg of Vecuronium. Patients were ventilated with Isoflurane (2%) in oxygen using circle absorber system. Just before laryngoscopy, anterior part of the hard cervical collar was removed, and the spine immobilization was maintained using MILS by an assistant anesthesiologist. All the intubations were performed (as per the manufacturer recommendations) by an experienced anesthesiologist, who had done at least 30 intubations, with each device. All standard PVC-made endotracheal tube (ET tube) 8.0 was used for males and size 7.0 for females. The ET tube was pre-shaped to the shape of C type, D type, or King Vision blade using a rigid stylet.
The laryngeal view was assessed using Cormack – Lehane grade (CL grade) [
Statistical testing was conducted with statistical package for the social science system SPSS version 16.0 (Chicago, IL, USA). Results on continuous measurements are presented on Mean ± SD (Min–Max) and results on categorical measurements are presented in Number (%). Significance is assessed at 5% level of significance. Analysis of variance (ANOVA) has been used to find the significance of study parameters between three or more groups of patients, Post-Hoc Tukey test has been employed to find the pairwise significance between groups. Chi-square/Fisher Exact test has been used to find the significance of study parameters on categorical scale between two or more groups.
Visualization of the glottis
Cormack–Lehane grading and POGO scores were used for visualizing the glottis. Good grade visualization (CL grade 1 and 2) of the vocal cords was obtained in all the patients in three groups [
Glottis view is also assessed using POGO score. The mean POGO scores were comparable in group C and group K [
Success of intubation
Intubation was successful in all patients (100%), using all three devices [
Time for intubation
Times for passing of VL through incisors to visualization of passing of ET tube through glottis and also for appearance of ETCO2 tracing were noted with these devices [
Ease of insertion of laryngoscope
The curvatures of laryngoscope blades are different with King Vision and C and D blades of C-MAC devices. Hence ease of insertion was noted based on 5 point Likert scale [
Intubation difficulty score
An IDS indicates the degree of difficulty of intubation. IDS scores were comparable in group C and group K (P = 0.34) [
Alternative techniques used
Only few patients required laryngeal manueuver (2, 3, and 5 in group C, K, and D, respectively) for aiding the passage of the endotracheal tube (ET) through glottic opening (P > 0.05). In one patient in group K, bougie assisted endotracheal tube insertion was done.
One patient in group K had bronchospasm, following ET tube insertion and was managed according to our institute protocol.
In patients with cervical spine injury with cervical immobilization, endotracheal intubation by direct laryngoscope is difficult due to poor visualization of glottis. In these scenarios, where alignment of oropharyngeal and laryngeal axes is not possible, indirect laryngoscopes such as videolaryngoscopes play a vital role in providing optimal glottis view, without movement of cervical spine. Though C-MAC conventional blade and D blades have been used in simulated difficult airway scenarios with cervical immobilization,[
The available literature for use of videolaryngoscope is in simulated difficult airway scenarios such as, hard collar or MILS maneuver in patients with normal airways or as a teaching/testing material on manikins.[
Optimal visualization of the glottis is important for the success of intubation with nil/restricted spine mobility. In our study, CL grade 1 visualization was obtained in 36 (80%), 32 (72%), 34 (76%) patients with conventional C-MAC, KVVL, and D blade C-MAC videolaryngoscope, respectively. A good grade of glottis visualization (CL grade 1 and 2) was obtained in all patients. In a manikin-based study with cervical immobilization by Kılıçaslan et al., good grade view (CL grade 1 and 2) was obtained by all the laryngoscopists.[
The CL grading system has numerous problems. The grades are ambigious between grade 1 and grade 2.[
Success of intubation
Better visualization of the glottis does not necessarily imply improved first attempt success of endotracheal intubation using VL owing to unique curvature of the blades. We used styleted ET tube, preshaped to the blade of particular VL for better visualization of the tip of the ET tube. First attempt success was noted in 100% (45/45), 93.3% (42/45), 95.6% (43/45) of the patients using conventional blade C-MAC, KVVL, and D blade C-MAC videolaryngoscopes, respectively [
The prolonged apnea time and delayed intubation can lead to hypoxemia and desaturation in patients. Because the tube was visualized passing through the glottis, we measured both the times; (a) time from scope insertion to tube passing the glottis and (b) time from scope insertion to appearance of first ETCO2 tracing on the monitor. The mean intubation times were comparable in conventional C-MAC and KVVL (23 vs. 24 s) and KVVL and D blade C-MAC (24 vs. 26 s) [
One of the prerequisites for the successful laryngoscopy and subsequent intubation in patients with cervical immobilization is ease of insertion of laryngoscope blade. We graded the ease of insertion of laryngoscope blade as 1 to 5 (1, very easy to 5, very difficult). The ease of insertion of conventional C-MAC was significantly better as compared to KVVL and D blade C-MAC VL [
The factors which determine difficulty of intubation are number of attempts, number of operators, alternative technique used, glottis exposure, application of lifting force external pressure, and the vocal cord position. The intubation difficulty score[
In the present study, all the patients were intubated after induction of general anesthesia with MILS. Therefore, no post intubation neurologic assessment was done to know the effectiveness of these devices in preventing further neurological injury due to laryngoscopy and intubation.
In the present study, King Vision videolaryngoscopy, conventional C-MAC, and D blades were assessed for first attempt success of intubation, time for intubation, and glottic visualization.
All the three videolaryngoscopes provided good first attempt intubation success Intubation times were faster with conventional C-MAC as compared to D blade of C-MAC. King Vision videolaryngoscope and conventional C-MAC had comparable intubation time All the three videolaryngoscopes provided good grade glottic visualization The ease of insertion of laryngoscope blade is graded as conventional C- MAC > King Vision > D blade C-MAC videolaryngoscopes.
All the three videolaryngoscopes provided good first attempt intubation success
Intubation times were faster with conventional C-MAC as compared to D blade of C-MAC. King Vision videolaryngoscope and conventional C-MAC had comparable intubation time
All the three videolaryngoscopes provided good grade glottic visualization
The ease of insertion of laryngoscope blade is graded as conventional C- MAC > King Vision > D blade C-MAC videolaryngoscopes.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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