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Comparison of video laryngoscope with direct laryngoscope for endotracheal intubation by cardiology residents: A randomized cross-over manikin-based study
Correspondence to VIBHAV SHARMA; dr.vibhav90@gmail.com
[To cite: Yadav S, Sharma V, Gupta N, Parashar N, Ramachandran R, Roy A. Comparison of video laryngoscope with direct laryngoscope for endotracheal intubation by cardiology residents: A randomized crossover manikin-based study. Natl Med J India 2025;38:264–7. DOI: 10.25259/NMJI_1141_2023]
Abstract
Background
Critically ill cardiac patients may decompensate suddenly owing to arrhythmias and worsening haemodynamics, often necessitating emergent endotracheal intubation. Training in airway management is usually neglected for residents in the cardiac intensive care unit (ICU). There is an unmet need to train cardiology residents in the swift management of airways in the acute setting of a cardiac arrest.
Methods
In this manikin-based cross-over study, we compared King’s vision channelled (KVC) and non-channelled video laryngoscopes (King’s vision [KV]) with Macintosh direct laryngoscopes (DL) for endotracheal intubation by 89 resident doctors, predominantly cardiology residents. All participants performed endotracheal intubation by all three types of laryngoscopes after a didactic training session. The primary endpoint of the study was time to endotracheal intubation. Other parameters assessed were best glottic view, time to glottic view, ease of use of the device, failed attempts and retention of skills over 6 months.
Results
Total time to tracheal intubation was least with KVC, 10.0 (interquartile range [IQR] 6.0–10.0) seconds, as compared to KV, 15.0 (IQR 12.0–17.5) or DL, 24.0 (IQR 22.0–30.0) seconds (p<0.001). Both types of video laryngoscopes provided superior glottic view and had lower failure rates (p<0.001). KVC video laryngoscope and Macintosh DL were relatively easier to use (p<0.001). KVC and KV provided better retention of skills at 6 months.
Conclusion
Cardiology residents who were novices in endotracheal intubation took the least time for intubation on manikin with the KVC video laryngoscope when compared with the KV video laryngoscope and Macintosh DL. Further, real-life studies are needed to assess any difference in clinical situations.
INTRODUCTION
Critically ill cardiac patients suffering a cardiac arrest have a very narrow window for resuscitation due to their poor haemodynamic reserve. Moreover, the procedure of endotracheal intubation itself exposes the patient to significant haemodynamic stress secondary to changes in blood pressure, heart rate, and systemic vascular resistance.1 An emergent procedure in the setting of a cardiac arrest carries major risk as compared to elective intubations performed by trained anaesthesiologists. Hence, cardiologists working in cardiac intensive care units should be reasonably proficient in endotracheal intubation. In clinical practice, endotracheal intubations are most often done under direct laryngoscopy (DL) using the Macintosh laryngoscope due to its simplicity, low cost and familiarity. Video laryngoscopy is a relatively newer technique. A video laryngoscope has a camera at its tip which provides live images of the glottis and theoretically improves rates of successful endotracheal intubation by optimising the glottic view independent of the ability to bring the glottis in line with the oral cavity. However, there are a few potential disadvantages of a video laryngoscope, such as obscuration of the view due to fogging and secretions, which may require pre-suctioning to clear the airway of the secretions and a greater cost of purchase and maintenance as compared to a direct laryngoscope (DL).2
Cardiology residents in intensive care units (ICU) are usually not trained in emergency endotracheal intubations. In the 19-bedded cardiac ICU of this tertiary care centre, the incidence of endotracheal intubation in the past 6 months was 137 of 1532 patients admitted. Endotracheal intubation is an essential part of advanced cardiac life support which has a major impact on patient survival. The incidence of severe hypoxaemia during endotracheal intubation in ICUs is 9.3%. Hypoxaemia, when added to the already compromised cardiovascular status of patients in cardiac ICUs, can have deleterious effects.
With this unmet need of training cardiology residents in the life-saving skill of endotracheal intubation and considering the contradictory evidence in favour of the superiority of video laryngoscopy over DL, we undertook this manikin-based study to assess the efficacy and ease of use of a video laryngoscope versus a DL amongst cardiology residents at a tertiary care cardiology centre.3,4 We aimed at exploring which amongst the three devices, channelled and non-channelled video laryngoscope (King Vision, AMBU Inc., Copenhagen, Denmark) (King’s vision channelled [KVC] and King’s vision [KV]) and DL should be the device of choice for cardiology residents to learn endotracheal intubation on manikins to achieve minimal intubation time.
METHODS
Study design and participants
This was a randomized cross-over manikin-based study done amongst 89 resident doctors, predominantly from cardiology, who did not have any prior formal training in airway management and consented to participate in the study. Cardiology, pulmonary medicine, geriatric medicine and internal medicine residents participated in the study. Anaesthesia residents were excluded. A written multiple-choice question based test was give to assess the baseline knowledge of the study participants, following which they received a standardized content (study material with video presentation) for at least 30 minutes followed by a demonstration of endotracheal intubation by a video laryngoscope KVC, KV and Macintosh DL by a physician with expertise in all three. The presentation comprised a review of airway anatomy, the study protocol and features of the three types of laryngoscopes.
Video laryngoscopes are available in two designs— channelled and non-channelled. The channelled video laryngoscopes have a channel in their blade which incorporates the endotracheal tube, so the tip of the endotracheal tube is under vision throughout its transit, whereas in the non-channelled design, the tip of the tube can only be seen once it reaches the glottis, and hence, there is a potential to cause injury to the soft tissues of the oropharynx. All the residents were allowed to practice for 10 minutes with all three laryngoscopes on manikin (Laerdal airway management trainer [Laerdal Inc., Stavanger, Norway]) until they were comfortable with the devices and had at least three successful intubation attempts with each device. The residents were allowed to ask questions at any time during the practice session and feedback was provided by the instructor.
This was followed by an assessment of their skill and knowledge. Participants initially performed two intubation attempts using the DL and then with each of the two video laryngoscopes. Participants were free to place the monitor as they preferred for optimal viewing. All attempts were measured using a stopwatch. The better of the two readings was recorded.
Tracheal intubation skills with the devices were assessed using the Laerdal airway management trainer (Laerdal Inc., Stavanger, Norway) in a normal airway in the supine position. The glottic views during the attempts were assessed using the percentage of glottic opening (POGO) score and modified Cormack–Lehane (CL) grade. All participants rated ease of obtaining a glottic view, ease of blade insertion, ease of guiding the tube to the glottis, ease of intubation and overall experience on a 5-point Likert scale (very easy, easy, neutral, hard or very hard). At the end of each session, each participant scored the ease of use of each device on a visual analogue scale (from 0 extremely easy to 10 extremely difficult). At the end of 6 months, all the participants attempted intubation in the same manikin with the same devices without any repeat didactic teaching or practice. This was done to mimic the clinical scenario where medical personnel are called infrequently to perform tracheal intubation urgently.
The study was registered with the Clinical Trials Registry— India (REF/2020/09/036974) and was approved by the Institutional Ethics Committee at AIIMS, New Delhi (IEC-923/04 September 2020).
Outcome measures
The primary outcome measure was the time to tracheal intubation which was defined as the time from insertion of the blade between the teeth until the tracheal tube was deemed to be positioned correctly by each participant. A failed intubation attempt was defined as an attempt in which the trachea was not intubated or oesophageal intubation occurred or when the time to intubate exceeded 120 seconds. Secondary outcome measures were time to glottic view, rate of successful placement of the tube in the trachea, self-assessment of the functionality of the afore-mentioned devices, including operator satisfaction and the degree of retention of the skills over 6 months.
Statistical analysis
The sample size was calculated on the basis of a previous study by Rendeki et al.4 The mean time for intubation using a DL and KV channelled blade (assuming the same time for a non-channelled blade as well) was 15 and 12.5 seconds, respectively, with a standard deviation (SD) of 6 seconds in each group. Considering 1% level of significance and a power of 90% (as there are three pair-wise comparisons), a sample size of 90 was calculated using a paired t-test design. Finally, the study recruited 89 participants.
Data for the success of tracheal intubation attempts were analysed using the Chi-square or Fisher’s exact test as appropriate. Data for the duration of the first and the successful intubation attempt and the instrument difficulty score were analysed using the paired t-test. The number of intubation attempts, the number of optimization manoeuvres used, and the severity of dental trauma were analysed using the Mann– Whitney rank sum test. Continuous data are presented as mean (SD), and ordinal and categorical data are presented as raw numbers and as frequencies. The level for all analyses was set as p<0.05.
RESULTS
A total of 89 cardiology resident doctors participated in the study. Visualization of the glottis as assessed by the CL grade was better with the video laryngoscopes. Median CL grade with DL was 2, whereas with the video laryngo-scope, all the residents were able to obtain a CL grade of 1, both with channelled and non-channelled types and this difference was statistically significant (p<0.001). Median POGO score with DL was 75 (interquartile range [IQR] 72–80), with non-channelled blade (KV), it was 85 (IQR 80–90) and with channelled blades (KVC), it was 92 (IQR 90–95) and this difference was statistically significant when all the three modalities were compared with each other (p<0.001). Time to obtain an optimal glottic view was shortest with the channelled video laryngoscope (DL 8.0 [IQR 7.5–10] seconds, KV 4.0 [IQR 3.0–5.0] seconds and KVC 3.0 [IQR 2.0–5.0] seconds) and this difference was also statistically significant when comparisons were made between the three modalities (p<0.001). This difference in time to optimum glottic view also reflected similarly in total time to tracheal intubation which was also least with channelled blades (DL 24.0 [IQR 22.0– 30.0] seconds, KV 15.0 [IQR 12.0–17.5] seconds and KVC 10.0 [IQR 6.0–10.0] seconds) with the difference being statistically significant when the three modalities were compared with each other (p<0.001) for all the three modalities.
On a subjective assessment of the ease of use, there was no significant difference between the three types of laryngoscopes with respect to the ease of obtaining a glottic view DL 2.0 (IQR 1.0–2.0), non-channelled video laryngoscope 2.0 (IQR 1.0–2.5), channelled video laryngoscope 1.9 (IQR 1.0–2.0); p=0.119 overall. The residents found both DL and KVC laryngoscope equally easy to use (mean score 2.0 [IQR 1.0–2.0] for both, p=1.0), whereas they found the non-channelled laryngoscope relatively difficult to use 2.0 (IQR 2.0–3.0) (p=0.003 and 0.006, respectively, when compared with DL and channelled laryngoscope). This difference was mainly due to an ease of passing the blade into the glottis which was significantly easier with DL and channelled blade as compared to non-channelled blade (DL 2.0 [IQR 1.0–2.0], KV 2.0 [IQR 2.0–3.0], KVC 2.0 [IQR 1.0–3.0], DL vs. KV p<0.001, DL vs. KVC p=0.060 and KV vs. KVC p=0.009) and ease of passing the endotracheal tube into the trachea which was again significantly easier with DL and channelled video laryngoscope as compared to non-channelled video laryngoscope (DL 2.0 [IQR 1.0–2.0], KV 2.0 [IQR 2.0–3.0], KVC 2.0 [IQR 1.0–2.0], DL vs. KV p<0.001, DL vs. KVC p<0.011 and KV vs. KVC p<0.001). Successful intubation in the first attempt was highest with the channelled video laryngoscope (DL 0%, KV 29%, KVC 55%, p<0.001).
Repeat laryngoscopy and endotracheal intubations were performed similarly by all the residents 6 months later without repeating the training session and the results were similar to those obtained at baseline.
DISCUSSION
We observed that the cardiology residents found the KV channelled video laryngoscope more effective and easier to use than the KV video laryngoscopes, which, in turn, was better than conventional DL with the Macintosh laryngoscopes. Visualization of the glottis, as assessed by the Cormack– Lehane grade and POGO scores, was best with the video laryngoscopes as compared to DL, which is not surprising since the video laryngoscopes provide a view of the glottis irrespective of the ability to bring the airway in line with the oral cavity; thus, they may be better suited in emergent settings when adequate muscle relaxation is often not feasible. However, since this was a simulated study done on manikins, the effects of fogging of the lens in case of video laryngoscopes was not accounted for. These results duplicated the findings of another smaller manikin study done on 15 resident doctors by Murakami et al. in which video laryngoscopy offered better glottic view and lower failure rate as compared to DL.5 They also showed that the total intubation time was significantly shorter with the video laryngoscopes which was consequent to significantly shorter time to visualization of the glottis, and time from visualization of the glottis to placement of the endotracheal tube was not significantly different. This finding is also duplicated in our study which shows that time to optimum glottic view and total time to intubation are significantly lower with the video laryngoscopes. Similar results were also obtained in another manikin-based study by Rendeki et al.4 which recruited fifty medical students who were novices in endotracheal intubation. Their findings with respect to the extent of glottic view, time to tracheal intubation and ease of use also concurred with our findings.
On a subjective analysis of the ease of use of the three types of laryngoscopes in our study, we observed that there was no significant difference between the DL and KVC video laryngoscope and both were significantly easier than the KV video laryngoscope. This observation was consequent to difficulty in passing the tube upto the glottis in case of a KV video laryngoscope. This can be explained by the fact that during direct and channelled video laryngoscopy, the tip of the tube is in the field of view throughout its course, whereas in a non-channelled video laryngoscope, the tube is passed blindly upto the glottis before it appears in the field of view. This also predisposes to soft-tissue injury in the oral cavity and pharynx. In our study, the rate of successful intubation during the first attempt by novice users was highest for the channelled video laryngoscope which was also the finding in other studies mentioned. Another manikin-based study,6 which recruited 50 emergency medicine physicians, compared the performance of video laryngoscopy, with and without ongoing cardiopulmonary resuscitation (CPR), and showed the superiority of video laryngoscopy with ongoing CPR, in terms of shorter intubation times, ease of intubation, lower failure rate and better CL grade, again these results were same as our study.
As far as clinical data are concerned, there are conflicting data on the superiority of video laryngoscopy over DL, with some studies showing superiority of video laryngoscopy, whereas others point towards no added benefit of a video laryngoscope over DL.1,2 A systematic review and meta-analysis of 10 studies, by Nalubola et al. comparing the outcomes of video laryngoscopy versus DL amongst novice intubators,7 demonstrated an increased success rate and decreased time to intubation with video laryngoscopy. Four studies also showed a reduction in inadvertent oesophageal intubations. On further sub-analyses, it was found that these differences were seen only with channelled video laryngo-scopes, and only with intubations performed by the least experienced medical students as compared to others. These results were duplicated in our study. A 2016 Cochrane review that analysed 64 randomized controlled trials (RCTs) including a total of 7044 participants reported lower failure rates and lesser airway trauma with video laryngoscopy versus DL in the subgroup of patients with a difficult airway; however, out of the 64 studies only 3 comprised intubation done in the emergency setting, so the results are not generalizable to the subset of patients seen in the cardiac intensive care units.8 Another study done in the pre-hospital setting did not show any significant difference between first attempt success, overall success and Cormack–Lehane grade between video and DL.3 A recent review of six randomized trials concluded that there was no difference in first-pass endotracheal intubation success rate, time to endotracheal intubation and occurrence of oropharyngeal trauma for elective endotracheal intubations performed by experienced anaes-thesiologists.9 In a recent, large retrospective study of 14 387 non-trauma out-of-hospital cardiac arrest patients, video laryngoscopy has shown better neurological outcomes due to decreased hypoxaemia.10
Another meta-analysis of seven studies in the pre-hospital setting including a total of 23 953 participants suggested that there was a higher likelihood of first-pass success, greater overall success and a lower number of intubation attempts with video laryngoscopy.11 However, these two studies were limited by the inclusion of retrospective studies and significant heterogeneity. Our study is novel in the following manner. It has been done where residents were given a complete cognitive and psychomotor training package. Both the theoretical and practical aspects of endotracheal intubation were taught such that the self-assessment as well as the assessment of the procedure and equipment, was well-informed and valid. The study includes cardiology residents, and hence, the whole training programme with the conclusions about the device can be reproduced for similar training programmes for ICUs which are manned by nonanaesthesiologists or untrained airway proceduralists.
The clinical implications of our study are that video laryngoscopy may prove to be superior to DL for training of novices in critically ill patients thus shortening intubation time and improving patient outcomes. Furthermore, since there is no need to align the airways with the oral cavity for visualization of the glottis, it may be particularly useful in difficult situations such as obese patients, patients with a short neck or restricted mouth opening, or those with cervical spine instability. Although fogging of video laryngoscopes in real patients remains an issue, it is not known how this might affect outcomes compared to DL. Hence, there is a need to explore this in RCTs on real patients.
Limitations
There are inherent limitations of manikin-based study. Haemodynamic changes and airway trauma were not assessed. Hence, the results may not be generalizable to the actual clinical setting in terms of improved outcomes, such as successful resuscitation and neurological outcomes. Furthermore, the airway simulator used in our study simulated a normal airway, so the effects of varying grades of airway difficulty could not be assessed. The participants in our study were not truly novices to video laryngoscopy but had varying levels of exposure to DL as part of their prior medical training; this might have potentially affected our results.
Conclusion
We conclude that video laryngoscopy with channelled blades significantly decreased time to glottic view and tracheal intubation and provided better visualization of the glottis and a better operator experience overall. Hence, we recommend the use of video laryngoscopy over DL for training of novices.
ACKNOWLEDGMENT
The project was funded by research section at the All India Institute of Medical Sciences, New Delhi, India (AECIPN-AIIMS-2020-79).
Conflicts of interest
None declared
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