Comparison of endotracheal intubation with Macintosh versus King Vision video laryngoscope using coronavirus disease 2019 barrier box on manikins: A randomized crossover study
1Department of Trauma and Emergency, AIIMS, Bhubaneswar, Odisha, India
2Department of Anaesthesiology, AIIMS, Bhubaneswar, Odisha, India
Keywords: Coronavirus disease 2019, intubation, King Vision video laryngoscope, Macintosh laryngoscope, manikin
BACKGROUND: Coronavirus disease 2019 (COVID 19) virus usually spreads through aerosol and close contact. Frontline health care workers handle aerosol generating procedures like endotracheal intubation. To reduce this risk, COVID 19 barrier box came into the picture. However, the COVID 19 barrier box may compromise easy and successful intubation, and their limitation must be studied.
OBJECTIVES: The objective of this study was to assess the time to successful intubation with or without the COVID 19 barrier box using the Macintosh laryngoscope and King Vision video laryngoscope (KVVL). We also assessed the first pass success rate, ease of intubation, Cormack– Lehane (CL) grade, and requirement of external laryngeal manipulation.
METHODS: We conducted this manikin based randomized crossover study to assess the time to successful intubation by anesthesiologists (22) and emergency physicians (11) having 1 year or more experience with or without COVID 19 barrier box by using the Macintosh laryngoscope and KVVL. Our study randomized the sequence of the four different intubation scenarios.
RESULTS: The comparison of mean duration of intubation between KVVL (13.21 ± 4.05 s) and Macintosh laryngoscope (12.89 ± 4.28 s) with COVID 19 barrier box was not statistically significant (95% confidence interval: 1.21–0.97). The ease of intubation, number of attempts, and requirement of external laryngeal manipulation were not statistically significant. Intubations were statistically significant more difficult with barrier box in view of higher CL grade.
CONCLUSION: Time to intubation was longer with COVID 19 barrier box using KVVL as compared to Macintosh laryngoscope which was statistically not significant.
Coronavirus disease 2019 (COVID 19) was declared as pandemic by the WHO on March 11, 2020. The causative organism of the disease (severe acute respiratory syndrome coronavirus 2) usually spreads through droplets and aerosols. Various aerosol generating procedures such as endotracheal intubation and bag mask ventilation are being performed by frontline health care workers. The COVID 19 pandemic is continuing and creating serious challenges to the health care personnel involved in airway management. Various tools have been invented to curtail this risk to the person managing the airway, like the aerosol box. The COVID 19 barrier box covers the patient’s head and neck and effectively reduces the aerosol spread during endotracheal intubation.[3 5] Further, the COVID 19 barrier box without negative pressure may increase the risk to patients and health care providers.[6 9]
Although the need for a change in intubation practice through barriers to reduce the aerosol spread is apparent, it will not be without a learning curve. The Macintosh laryngoscope is used commonly in the emergency department, intensive care units, and operation theater. The King Vision video laryngoscope (KVVL) (AMBU, Denmark) is another portable, inexpensive, and suitable option for the emergency department. Using these laryngoscopes with the aerosol box may compromise easy and successful intubation. Therefore, their limitations or benefits must be studied.
We conducted this manikin based study to assess the time to successful intubation by anesthesiologists and emergency physicians having 1 year or more experience with or without aerosol box using the Macintosh laryngoscope and KVVL. We also assessed the first pass success rate, ease of intubation, Cormack– Lehane (CL) grade, and requirement of external laryngeal manipulation.
Material and Methods
This study was a manikin based randomized crossover study. After getting approval from the Institute Ethics committee (IEC NO T/IM NF/TandEM/20/39 dated November 12, 2020), it was registered in the Clinical Trials Registry India (CTRI/2021/02/031052).
Participants were the faculty members and residents of the anesthesia and emergency medicine departments who had experience of intubation for more than 1 year and familiar with using both KVVL and Macintosh laryngoscope. Participant refusal was taken as exclusion criteria. Written informed consent was obtained from each participant before the study.
The participants practiced intubation 20 times on manikin with COVID 19 barrier box: 10 times using Macintosh laryngoscope and 10 times using KVVL after demonstration by the investigators (SS, UH, CM, NS, and SD). The intubation was done in a simulated environment. The Airway Trainer Manikin (Laerdal Medical, Stavanger, Norway) was used for practice and study. The COVID 19 barrier box used was a modified version of the basic model by Sahoo et al.[10,11] [Figure 1]. In the basic model, visualization of the vocal cord was not proper due to the right angle joint. Hence, the height of the vertical wall and the length of the horizontal roof were decreased, and an additional slanting roof was made, which improved the visualization of the vocal cord. Moreover, the creation of side opening helped in providing backward upward rightward pressure, suction, and bougie. All the participants were acquainted with the COVID 19 barrier box before doing the study. All intubations were done using either a size 3 Macintosh blade or channeled version of the KVVL blade, with a cuffed 7.5 mm internal diameter endotracheal tube (Smiths Medical, St. Paul, MN, USA). The lubricant was used with both the blade and the endotracheal tube while using the KVVL. An investigator was there to help with the equipment or external laryngeal manipulation on request. Timekeeping was done by the person not involved in the study during both practice and study intubations. We recorded the intubation time in seconds, the number of attempts, any need for external laryngeal manipulation, ease of intubation, and CL grade.
Randomization and blinding
A computer generated simple random sequence was used to assign study participants to four different scenarios. This randomization only ensured the intubation sequence of different scenarios (A, B, C, and D) [Figures 2 and 3]. It was an open level randomized crossover study.
Scenario A: Intubation with Macintosh laryngoscope without COVID 19 barrier box.
Scenario B: Intubation with Macintosh laryngoscope with COVID 19 barrier box.
Scenario C: Intubation with KVVL without COVID 19 barrier box.
Scenario D: Intubation with KVVL with COVID 19 barrier box.
The primary outcome was the time required for successful intubation, defined as the time duration from the insertion of the laryngoscope blade to the first lung inflation using a self inflating resuscitation bag after endotracheal tube cuff inflation. The secondary outcomes include ease of intubation, number of attempts, requirement of external laryngeal manipulation, and CL grading.
Sample size calculation
A study by Park et al. reported that the time for successful intubation using Macintosh direct laryngoscopy was 20 s, with a standard deviation of 10 s. The sample size was calculated to detect a 5 s difference with an alpha value of 0.05 and power of 80%. A sample size of 33 was required to achieve the required power.
Data were analyzed in SPSS version 27 (IBM Corp., Armonk, New York, USA). Categorical variables were expressed in frequency and percentages, and continuous variables were expressed in mean (standard deviation) or median (interquartile range [IQR]). The normality of the continuous variables was assessed using Shapiro– Wilk’s test, and except for age and years of experience, all the variables were normally distributed. Pairwise comparison of dichotomous variables was performed using McNemar’s test, and for multinomial variables, marginal homogeneity test was used. Comparison between two means was carried out using the paired sample t test. The 95% confidence intervals (CIs) were also calculated for the differences. Spearman correlation test was used to analyze the correlation between duration of intubation and years of experience.
The median age of the performing physicians was 30 years, ranging from 24 to 42 years. The majority were male (26, 78.8%). Out of the 33 physicians included in the study, 9 (27.3%) were teaching faculty, and 24 (72.7%) were residents. Among them, 11 were emergency physicians, while 22 were anesthesiologists. The median years of experience was 4 years (IQR [25th– 75th percentile]: 2.25–7) [Table 1].
The comparison of mean duration of intubation using Macintosh blade with (12.89 ± 4.28 s) and without (11.82 ± 4.25 s) COVID 19 barrier box was not statistically significant (95% CI: 0.04–2.18) [Table 2]. The comparison of mean duration of intubation with KVVL laryngoscope with(13.21±4.05 s) and without(12.08±3.73 s) COVID 19 barrier box was not statistically significant(95% CI: 0.47–1.85) [Table 3]. Similarly, we did not find any statistically significant difference between the Macintosh laryngoscope and KVVL with barrier box (95% CI: 1.21– 0.97) [Table 4]. Ease of intubation, number of attempts, and requirement of external laryngeal manipulation were not statistically significant with or without the COVID 19 barrier box. Second intubation attempts were required three times each for both the laryngoscopes with barrier box. There was a statistically significant higher CL grade (CL Grade 2) in case of Macintosh laryngoscope compared to KVVL with COVID-19 barrier box (95% CI: 0.06–0.52). There was a significant correlation between the duration of intubation with Macintosh laryngoscope and the years of experience (r= −0.420), but weak correlation between the duration of intubation with KVVL and years of experience (r = −0.146) [Figure 4].
We did not find any significant difference in the intubation time with the Macintosh laryngoscope blade and KVVL with or without the COVID 19 barrier box. With the COVID 19 barrier box, the average duration of intubation using KVVL was 13.21 ± 4.05 s, whereas the duration was 12.89 ± 4.28 s with the Macintosh laryngoscope. Intubations were statistically significant more difficult with barrier box in view of higher CL grade.
The duration of intubation was more with Macintosh laryngoscope using COVID barrier box in participants having less year of experience, but the year of experience had no correlation with KVVL.
Fong et al., in their randomized crossover manikin based simulation study using the aerosol box with GlideScope, found that the aerosol box increased the intubation time by 6 s which was not statistically significant. They also reported that the aerosol box could be an adjunct to personal protective equipment(PPE) to reduce the aerosol spread. Our study found that COVID 19 barrier box increased intubation time in both Macintosh laryngoscope and KVVL, but it was not statistically significant.
Kannaujia et al. had done a simulation study on manikin found no significant difference in intubation time, glottic view, and the first pass success rate with or without the aerosol box using GlideScope video laryngoscope, which was similar to our study. However, the participants included in their study were senior consultant anesthesiologists, while we included both residents and consultants of both anesthesia and emergency departments, which is more generalizable.
Abolkheir et al. had done a manikin study, found time to intubation was more with GlideScope than Macintosh laryngoscope which was similar to our study.
Our study also got similar findings to a few other studies conducted in real patients with COVID negative status. The barrier box did not cause delay in intubation time in a non-inferiority trial comparing with and without barrier box. In prospective trials by Jen et al. and Sahoo et al. in COVID 19 negative patients with normal airways, the use of the COVID 19 barrier box did not significantly delay the intubation time nor decrease the first pass success rate.[17,18]
During this COVID era, the role of PPE was crucial for health care providers’ safety. Shortage of PPE was also seen in a few places because of its extensive use during patient care. The idea of improving safety leads to the development of the barrier box.
Unlike Begley et al., we have not studied the PPE breach in our manikin study due to resource constraints. We have not studied the difficult airway scenarios and the degree of aerosol spread in our study. As the study has been done in simulated environment, the results may differ in clinical scenario. However, our findings are similar to few clinical studies. All the participants have more than 1 year of experience, and findings may be different when used by novice residents during airway management. We have not studied the effect of other types of protective barriers such as hoods and tents. The results from this study may not be generalizable to other design of COVID 19 barrier box.
The time to intubation was more with the COVID 19 barrier box using with KVVL than Macintosh laryngoscope which was not statistically significant. Hence, both Macintosh laryngoscope and KVVL can be used for intubation with a COVID barrier box. Further randomized control trials with a larger sample size may be considered in COVID 19 positive patients to validate these data with a barrier box.
How to cite this article: Guru S, Singh N, Sahoo S, Hansda U, Mohanty C. Comparison of endotracheal intubation with Macintosh versus King Vision video laryngoscope using coronavirus disease 2019 barrier box on manikins: A randomized crossover study. Turk J Emerg Med 2022;22:149-55.
This protocol was approved by the Ethics Committee of AIIMS, Bhubaneswar, Odisha, India, IEC NO‑T/IM‑NF/T&EM/20/39 dated November 12, 2020.
SS: conceptualization; data curation; formal analysis; methodology; project administration; resources; supervision; validation; writing – review and editing. NS: data curation; investigation; methodology; visualization; writing – original draft: data curation; investigation; visualization; writing – original draft; writing – review and editing. UH: data curation; visualization; writing – original draft; writing – review and editing. CM: methodology; data curation; investigation; visualization; writing – original draft; writing – review and editing. SG: methodology; data curation; investigation; visualization; writing – original draft; writing – review and editing.
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We would like to thank the Council of Scientific and Industrial Research– Institute of Minerals and Materials Technology, Bhubaneswar, for designing the COVID barrier box.