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 Table of Contents  
Year : 2019  |  Volume : 2  |  Issue : 1  |  Page : 10-16

Comparison of channelled blade with non-channelled Blade of King Vision™ videolaryngoscope for orotracheal intubation: A randomised, controlled, multicentric study

1 Department of Anaesthesia, Isha Multispeciality Hospital, Vadodara, Gujarat, India
2 Department of Anaesthesia, VINS, Vadodara, Gujarat, India
3 Department of Anaesthesia, KCHRC, Muni Seva Asharam, Goraj, Vadodara, Gujarat, India

Date of Web Publication25-Apr-2019

Correspondence Address:
Dr. Amit Shah
Department of Anaesthesia, Isha Multispeciality Hospital, Vadodara, Gujarat
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ARWY.ARWY_8_19

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Introduction: We conducted a randomised, controlled, prospective, multicentric comparison of channelled blade versus non-channelled blade of the King Vision™ videolaryngoscope for orotracheal intubation. Patients and Methods: A total of 66 patients included in the study were divided into two groups as follows: Group CH for intubation with channelled blade and Group NC for intubation with non-channelled blade. We compared the intubation time, ease of intubation and best laryngeal view obtained. Ease of intubation was categorised into ease of device insertion and ease of passage of endotracheal tube. Various impingements which occurred at the laryngeal inlet were observed and manoeuvres used to accomplish intubation were noted. Results: The grade of laryngeal exposure and time of laryngeal exposure were similar in both types of blade. We found a shorter intubation time of 15.24 ± 10.6 s in Group CH, whereas it was 28.57 ± 14.09 s in Group NC (P < 0.001). Impingement of the endotracheal tube at the glottic inlet was similar in both the groups, but manoeuvring of the device was not needed after laryngeal exposure in the case of the non-channelled blade. Manoeuvres needed to accomplish successful intubation were different in each group. Intubation with channelled blade requires anticlockwise rotation of the endotracheal tube as it is advanced in the slot while slight withdrawal and redirection towards the centre was needed most often with the non-channelled type of blade. Conclusions: We conclude that when used with the channelled blade, the King Vision videolaryngoscope requires shorter intubation time as compared to its use with the non-channelled blade. Anticlockwise rotation of the advancing endotracheal tube within the channel slot overcomes major impingement at the larynx and facilitates intubation with the use of channelled blade while slight withdrawal and redirection towards the centre are needed for successful intubation using the non-channelled blade.

Keywords: Channelled blade, ease of intubation, intubation time, manoeuvring, non-channelled blade, tube impingement, videolaryngoscopy

How to cite this article:
Shah A, Patwa A, Burra V, Shah D, Gandhi B. Comparison of channelled blade with non-channelled Blade of King Vision™ videolaryngoscope for orotracheal intubation: A randomised, controlled, multicentric study. Airway 2019;2:10-6

How to cite this URL:
Shah A, Patwa A, Burra V, Shah D, Gandhi B. Comparison of channelled blade with non-channelled Blade of King Vision™ videolaryngoscope for orotracheal intubation: A randomised, controlled, multicentric study. Airway [serial online] 2019 [cited 2023 Sep 21];2:10-6. Available from: https://www.arwy.org/text.asp?2019/2/1/10/257052

  Introduction Top

The inability to establish a definitive airway as being responsible for major airway-related morbidity and mortality was first described by Caplan et al in 1990.[1] The inability to intubate was one of the major causes of the problem and later development was focussed towards improving the intubation success rate. Development of the videolaryngoscope is one major step in the direction of improving the success rate of intubation. Development of videolaryngoscope technology brought about improvement in visualisation of the larynx, especially in patients with a difficult airway, because of the ability of videolaryngoscope devices to achieve laryngeal visualisation with lesser lifting force.[2],[3] Videolaryngoscopes also increased the field of vision and provided the ability to see around the corner, especially in the case of anatomically-shaped devices. The quest to improve visualisation has also brought its own share of problems. Numerous types of devices with different designs have been developed such as the Macintosh type (C-MAC), hyperangulated devices such as the GlideScope or devices with a dedicated channel such as the King Vision. Each type of device has its own technique of use and a learning curve for successful intubation.[3]

Channelled videolaryngoscopes provide the advantage of a dedicated passage for directing the endotracheal tube, removing the need for the stylet to direct the tube towards the glottic opening. However, there are certain situations where a channel may not be helpful and one needs a non-channelled type of device. Most videolaryngoscopes are either channelled or non-channelled, with both types of the blade not being present in the same device.[3] Studies have been undertaken to compare various devices with a different type of designs.[4],[5]

The King Vision™ videolaryngoscope has both channelled and non-channelled blades. The device is designed such that the channelled and non-channelled blades have similar angles. Channelled devices provide a dedicated passage to guide the endotracheal tube that facilitates faster intubation. The non-channelled device requires smaller mouth opening and has more room for manoeuvring for oral and nasotracheal intubation. It, however, requires a stylet to direct the endotracheal tube towards the glottic opening. There is no evidence in literature that compares channelled and non-channelled blades of the King Vision videolaryngoscope for orotracheal intubation.[6]

We aimed to compare the channelled and non-channelled blades of King Vision™ videolaryngoscope for laryngoscopy, intubation time and ease of laryngoscopy. The study objectives included the identification of difficulties encountered during videolaryngoscopy and techniques to overcome such difficulties.

  Patients And Methods Top

A randomised, controlled and prospective, multicentric study was conducted using the King Vision videolaryngoscope (channelled and non-channelled blades) on 66 patients in the age group of 18–60 years belonging to the American Society of Anesthesiologists Physical Status I, II, and III scheduled to undergo elective surgery. Other criteria to be satisfied before inclusion were a height of >150 cm and a weight of >30 kg. Exclusion criteria were mouth opening <18 mm and neck contractures. Informed consent was obtained from all patients. The study design was approved by the Ethical Committee.

Data generated from a pilot study was used to determine sample size. The time taken for endotracheal intubation was 24.0 ± 7.5 s with the non-channelled blade, whereas it was 13.8 ± 8.0 s with the channelled blade. With a mean difference of 10.2 s, the standardised effect size was 1.40. Assuming an alpha error 0.05, a power of 95 and standardised effect size of 1.40, the sample size arrived at was 27 in each group. We added 20% additional patients for possible attrition due to follow up, thereby obtaining a number of 33 patients in each group. Final data collection was done during a 6-month period using the King Vision videolaryngoscope (channelled blade and non-channelled blade).

On arrival of the patient in the operation theatre and after obtaining written informed consent, randomisation was done. After a thorough preanaesthetic evaluation, the patient was assigned to one of the two groups, Group CH for channelled blade and Group NC for non-channelled blade, using sealed envelope method. Basic monitoring was established that included 5-electrode electrocardiogram monitoring Lead II and V5, noninvasive blood pressure, pulse oximetry and capnography.

All patients satisfying the inclusion criteria were premedicated with glycopyrrolate 0.2 mg IV and fentanyl 2 μg/kg. The patient was positioned supine with the neck in a neutral position and preoxygenation was done for 3 min using a face mask connected to a closed circuit primed with 100% oxygen at a fresh gas flow of 6 L/min. Intravenous induction of anaesthesia was performed with injection propofol 2–2.5 mg/kg and injection succinylcholine 2 mg/kg. Following confirmation of complete muscle paralysis, videolaryngoscopy was performed with King Vision videolaryngoscope (channelled blade for Group CH and non-channelled blade for Group NC). The technique of intubation followed for both blades was as recommended by the company. The operator was allowed to change the patient's head and neck position in order to achieve optimum laryngeal view. This laryngeal view was graded using the modified Cormack and Lehane (CL) grading.

Ease of insertion of laryngoscope was judged by the operator, considering inability to perform laryngoscopy as score 0 while laryngoscopy performed with absolute ease as score 100. The time for laryngeal exposure was noted for both groups (laryngeal exposure time defined as time taken from introduction of blade past the incisors till optimal exposure of larynx). After achieving optimal laryngeal exposure, the endotracheal tube was gently slid from the side channel into the larynx in Group CH. For Group NC, a styletted, preshaped cuffed endotracheal tube of appropriate size (7.0 mm ID for females and 8.0 mm ID for males) was introduced into the oral cavity and advanced into the larynx. Time for intubation was noted for each patient. Intubation time was defined as the time taken from introduction of blade past the incisors to the passage of the endotracheal tube into the larynx till the black mark lay adjacent to the vocal cords.

Tube placement was confirmed by direct visualisation of the passage beyond vocal cords. Capnographic tracing was considered for final confirmation of the correct placement of the endotracheal tube. If direct visualisation was not possible (as evidenced by a CL Grade III or IV), the capnographic trace was considered as confirmation of intubation.

Intubation procedure was stopped if saturation dropped <95% or an unexpected technical problem was encountered. Mask ventilation was employed with 100% oxygen. Repeat attempts were made only after ensuring adequate oxygenation, relaxation and ensuring proper functioning of the device. If the endotracheal tube was not placed at an ideal depth within three attempts, the operator was allowed to use a different device for intubation. It was considered a failure if a device change was needed. Ease of insertion of endotracheal tube was judged by the operator, considering inability to intubate as score 0 while intubating with absolute ease as score 100.

During passage of endotracheal tube, site of impingement (right or left aryepiglottic fold, interarytenoid region, epiglottis and anterior subglottic area) was noted. During intubation, manipulations of scope (left/right rotation, withdrawal, lifting of scope) and manipulations of endotracheal tube were also noted (withdrawal of tube, 90° and 180° clockwise/anticlockwise rotation and then reversing same rotation, complete withdrawal and reinsertion). Use of adjuvants such as a gum elastic bougie in Group CH or changes required in the shape of the stylet in case of Group NC were noted. Other manipulations during the procedure such as rotation of the scope for introduction into the oral cavity, or change in the head-and-neck position while introducing the endotracheal tube or external laryngeal manipulation were noted. After the procedure, the blade of the King Vision videolaryngoscope was inspected for the staining of blood in order to evaluate oropharyngeal trauma during the procedure.

Anaesthesia was maintained with nitrous oxide in oxygen (50:50) with sevoflurane and atracurium infusion in appropriate doses. Antagonism of residual neuromuscular blockade was done at the end of surgery using injection neostigmine 50 μg/kg and injection glycopyrrolate 10 μg/kg IV. Following extubation, the endotracheal tube was inspected for blood staining in order to evaluate trauma that could have occurred during intubation.

Data were entered into a Microsoft Excel Sheet 2007 and data were analysed using MedCalc Version (MedCalc Software, Acacialaan 22,8400 Ostend, Belgium). Groups were compared with unpaired t-test and Chi-square test. Value of P < 0.05 was considered statistically significant.

  Results Top

Mean age in both the groups was comparable (P > 0.05) [Table 1]. Demographic variables such as gender and body mass index were also comparable between the two groups. All parameters of airway assessment such as abnormal dentition, neck circumference, hyomental distance, thyromental distance, difficult mask ventilation, interincisor gap, Mallampati score, upper lip bite test and neck extension) were comparable in both groups (P > 0.05).
Table 1: Demographic parameters

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The laryngeal exposure time was 7.84 ± 9.01 s in Group CH, whereas it was 5.27 ± 3.2 s in Group NC. The difference was not statistically significant (P > 0.05) [Table 2]. Both blades provide an almost equal laryngeal view as seen in [Figure 1]. The intubation time was 15.24 ± 10.6 s in Group CH, whereas it was 28.57 ± 14.09 s in Group NC. The difference was statistically significant (P < 0.001) [Table 2]. The time to successful intubation was significantly less when using the channelled blade as compared to the non-channelled blade. The channelled blade thus provides for rapid tracheal intubation when compared to the non-channelled blade.
Table 2: Laryngeal exposure time and intubation time

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Figure 1: Cormack-Lehane grade with channelled (CH) and non-channelled (NC) blades of King Vision videolaryngoscope

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As shown in [Table 3], the number of intubation attempts was similar in the two groups. Ease of insertion of the device was similar in both types of blade (P > 0.05). Ease of insertion of endotracheal tube was more with channelled as compared to the non-channelled blade, but the difference was statistically insignificant (P > 0.05).
Table 3: Difficulty scoring

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On analysing the type of impingement and manipulations needed for successful intubation [Table 4], the frequency of manipulations required to intubate were similar (39% for channelled vs 36% for the non-channelled blade). The type of manipulations needed was different with individual blades. Manipulation of the device was needed less frequently in the case of a non-channelled blade (16% vs 69%). Manipulation of the endotracheal tube was required with equal frequency in both types of blade (92% for channelled vs 91% for the non-channelled blade). The type of manipulation needed was different with individual blades. Anticlockwise rotation of the endotracheal tube was the most common type of manoeuvre (83%) in case of the channelled blade while withdrawing and redirecting it medially was the most common type of manoeuvre (90%) in the case of a non-channelled blade.
Table 4: Impingements and manipulations

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  Discussion Top

The videolaryngoscope improves glottic view and decreases failure of intubation, particularly among anticipated difficult airway.[3] The first true videolaryngoscope, GlideScope™ was developed as a hyperangulated blade to facilitate the difficulty faced with the so-called anterior larynx. Later on, to avoid the difficulty of inserting the endotracheal tube, angulated channelled videolaryngoscopes were designed. Simultaneously, cameras were incorporated into the Macintosh type of blade to make videolaryngoscopes similar to the conventional Macintosh type of videolaryngoscope. Almost all types of devices report an improved laryngeal view, but intubation techniques are different and require a different set of movements and skill set for successful intubation.[4]

Most videolaryngoscopes when designed were either hyperangulated non-channelled, angulated channelled or Macintosh type. Very few had incorporated two types of blade, especially channelled and non-channelled types. Previous studies comparing various types of devices, including channelled and non-channelled blades were undertaken.[5],[6],[7] Channelled blades reported shorter intubation times. However, no studies compared two different types of blades of the same device which has similar curvature and angles.

In our study, we compared channelled (Group CH) and non-channelled (Group NC) blades of the King Vision videolaryngoscope which demonstrated comparable laryngeal view and laryngeal exposure time (P > 0.05). There is a significant decrease in intubation time (P = 0.001) with greater ease of passing endotracheal tube using the channelled blade.

A study by Teoh et al. compared Pentax Airwayscope (AWS) with GlideScope and reported similar results, but their devices were different and there was significant design difference.[7] Furthermore, these authors have not reported the method of calculating the duration. They reported better laryngeal view with Pentax AWS (channelled device) as compared to the GlideScope (hyperangulated non-channelled device) though view should be either same or better with GlideScope. Our report of similar laryngeal views between both types of blades may be because of similar angles of both types of blade. Both types of device offered superior laryngeal view (97% having CL 1 or 2 views). This is consistent with the majority of the studies evaluating videolaryngoscopes.[7],[8],[9],[10] We reported shorter time for intubation with both types of the blades when compared with the study by Teoh et al. where Pentax AWS, C-MAC, GlideScope and Macintosh direct laryngoscopy were compared.[7] They reported an average 20 s time for intubation with channelled devices, whereas we reported an average of 15 s. The possible reasons could be a difference in the method of calculating the duration of intubation and also the difference in the technique of intubation. Pentax AWS was used like the Miller blade (with the blade including and lifting the epiglottis) and directing the tube towards a target while in the case of the King Vision videolaryngoscope, the recommended technique which we used was to keep the tip of the blade in vallecula and directing the tube to the centre of view allowing better trajectory. We also considered passage up to the black mark beyond vocal cords under vision on screen as an end point for successful intubation. With the advent of videolaryngoscopy where the passage of endotracheal tube into the trachea can be visualised and documented, earlier consideration of successful intubation as evidenced by a capnographic trace as an end point to denote successful intubation may be superfluous. We considered including the time taken for appearance of the capnographic trace if we could not identify the passage of black mark beyond vocal cords to calculate intubation time, but such calculations were not needed. Similar results were also reported by Tan et al. and Asai.[11],[12] Taylor et al. reported 35 s of median intubation time with McGrath angulated blade videolaryngoscope.[8] Our findings give a median duration for intubation of 24 s with a non-channelled blade which requires a similar technique of intubation. The possible reason could be the end point which was the passage of black mark up to the vocal cords in our study while removal of the device was used by Taylor et al. which may have increased the duration in their study. For adopting a new technique or device, ease of the procedure plays a major role. Videolaryngoscopy is a new tool which makes laryngoscopy easy, but the intubation could still be difficult. Thus, many authors comparing one device with the other have reported variable findings.

Despite comparable intubation duration and success with GlideScope and Macintosh laryngoscope, Lim et al. reported greater ease with GlideScope, especially in a difficult scenario. All anaesthesiologists would opt for the GlideScope in the future if given a choice.[13] When Savoldelli et al. compared the GlideScope, McGrath, Airtraq and Macintosh laryngoscopes, ease of procedure was the highest with Airtraq, a channelled videolaryngoscope device.[14] All other authors have compared only ease without identifying the specific element within the entire procedure. Ease of insertion of blade or device, when compared in our study, was similar because of similar angle of the channelled and non-channelled blades. This will remain true for all videolaryngoscopes of the channelled type or angulated devices such as Glidescope or C-MAC D-blade. The ease of passing endotracheal tube is likely to be better with channelled type of videolaryngoscope because of the presence of a dedicated passage compared to a non-channelled blade which requires a hyperangulated styletted within the endotracheal tube passed independent of the videolaryngoscope. In this study, ease of insertion was better with the channelled blade. The difference was not statistically significant possibly due to smaller sample size.

Easy passage of the endotracheal tube may require various manipulations to align tube trajectory with the laryngeal opening. Not many authors have identified the difficulties and manipulation which are needed for intubation procedure with a videolaryngoscope. Teoh et al. identified manoeuvres which were needed for the intubation procedure.[7] We have for the first time identified the impingement of the endotracheal tube at the laryngeal inlet as it is advanced and also documented various manipulations needed to accomplish intubation with a videolaryngoscope.

A total of 39% of patients had some form of impingement in the case of the channelled blade while 36% of patients had impingement with the non-channelled blade. Nearly 50% of impingement with the channelled blade occurred over the right aryepiglottic fold, whereas in the case of non-channelled blade, impingement occurred at various places such as epiglottis and anterior subglottic area including the right aryepiglottic fold. The possible reason for impingement occurring at the right aryepiglottic fold could be due to central insertion of device and introduction of the endotracheal tube from the right of the device. The reasons behind impingement to the anterior glottic structures, especially in the case of the non-channelled blade, could be due to the hyperangulated stylet required to position the endotracheal tube in front of the glottic opening.

With the channelled videolaryngoscope, manipulation of the device was needed in the majority of patients (69%) where impingement occurred. Only 16% of the patients where the non-channelled blade was used needed repositioning or manipulation after a satisfactory laryngeal view was obtained.

As the videolaryngoscope provides a view only beyond the curvature of tongue, it does not provide a view of the entire track taken by the endotracheal tube. This may necessitate some form of manipulation of the endotracheal tube to align its trajectory with the glottic opening in both types of videolaryngoscope. In the case of the channelled blade, anticlockwise rotation of the endotracheal tube as it slides off the dedicated slot redirects it towards left, almost always overcoming the impingement on the right aryepiglottic fold. This was needed in 83% of cases when impingement occurred. In the case of the non-channelled blade, withdrawal of the styletted endotracheal tube and redirection towards the centre was done most of the time (90%) to facilitate passage of the tube towards the glottic opening.

The major limitation of our study was that it was done at two institutes by four anaesthesiologists who were experienced with videolaryngoscopy. This could have resulted in better intubation times as compared to other studies. Ease of insertion can again be influenced by smaller sample size. On the basis of the results of our study, we recommend that a larger study is needed to identify not only the various impingement sites but also the possible manoeuvres needed to overcome difficulties caused by such impingements.

  Conclusion Top

We conclude that the channelled blade of the King Vision videolaryngoscope provides shorter intubation time as compared to the non-channelled blade. It is easier to perform intubation with a channelled videolaryngoscope. Anticlockwise rotation of the endotracheal tube as it is advanced along the channelled blade can overcome major impingements and facilitate intubation. While using the non-channelled blade, the styletted endotracheal tube needs to be slightly withdrawn and redirected towards the centre for better success at intubation.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Caplan RA, Posner KL, Ward RJ, Cheney FW. Adverse respiratory events in anesthesia: A closed claims analysis. Anesthesiology 1990;72:828-33.  Back to cited text no. 1
Russell T, Khan S, Elman J, Katznelson R, Cooper RM. Measurement of forces applied during Macintosh direct laryngoscopy compared with GlideScope® videolaryngoscopy. Anaesthesia 2012;67:626-31.  Back to cited text no. 2
Lewis SR, Butler AR, Parker J, Cook TM, Schofield-Robinson OJ, Smith AF. Videolaryngoscopy versus direct laryngoscopy for adult patients requiring tracheal intubation: A Cochrane Systematic Review. Br J Anaesth 2017;119:369-83.  Back to cited text no. 3
Kelly FE, Cook TM. Seeing is believing: Getting the best out of videolaryngoscopy. Br J Anaesth 2016;117 Suppl 1:i9-13.  Back to cited text no. 4
Teoh WH, Saxena S, Shah MK, Sia AT. Comparison of three videolaryngoscopes: Pentax Airway Scope, C-MAC, Glidescope vs. the Macintosh laryngoscope for tracheal intubation. Anaesthesia 2010;65:1126-32.  Back to cited text no. 5
Murphy LD, Kovacs GJ, Reardon PM, Law JA. Comparison of the king vision video laryngoscope with the Macintosh laryngoscope. J Emerg Med 2014;47:239-46.  Back to cited text no. 6
Teoh WH, Shah MK, Sia AT. Randomised comparison of Pentax Airwayscope and Glidescope for tracheal intubation in patients with normal airway anatomy. Anaesthesia 2009;64:1125-9.  Back to cited text no. 7
Taylor AM, Peck M, Launcelott S, Hung OR, Law JA, MacQuarrie K, et al. The McGrath® series 5 videolaryngoscope vs. the Macintosh laryngoscope: A randomised, controlled trial in patients with a simulated difficult airway. Anaesthesia 2013;68:142-7.  Back to cited text no. 8
Fong AW, Lam KC, Cheng BC, Lam KK, Chan MT. A randomised comparison of InnoScope and Macintosh laryngoscope in simulated difficult tracheal intubation in manikins. Anaesthesia 2013;68:167-74.  Back to cited text no. 9
Moore AR, Schricker T, Court O. Awake videolaryngoscopy-assisted tracheal intubation of the morbidly obese. Anaesthesia 2012;67:232-5.  Back to cited text no. 10
Tan BH, Liu EH, Lim RT, Liow LM, Goy RW. Ease of intubation with the GlideScope or Airway Scope by novice operators in simulated easy and difficult airways – A manikin study. Anaesthesia 2009;64:187-90.  Back to cited text no. 11
Asai T. Tracheal intubation with restricted access: A randomised comparison of the Pentax-Airway Scope and Macintosh laryngoscope in a manikin. Anaesthesia 2009;64:1114-7.  Back to cited text no. 12
Lim TJ, Lim Y, Liu EH. Evaluation of ease of intubation with the GlideScope or Macintosh laryngoscope by anaesthetists in simulated easy and difficult laryngoscopy. Anaesthesia 2005;60:180-3.  Back to cited text no. 13
Savoldelli GL, Schiffer E, Abegg C, Baeriswyl V, Clergue F, Waeber JL. Comparison of the Glidescope, the McGrath, the Airtraq and the Macintosh laryngoscopes in simulated difficult airways. Anaesthesia 2008;63:1358-64.  Back to cited text no. 14


  [Figure 1]

  [Table 1], [Table 2], [Table 3], [Table 4]

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