Macintosh laryngoscope versus AMBU King Vision video laryngoscope for endotracheal intubation using a COVID-19 barrier box: A randomized controlled trial.

BACKGROUND: Coronavirus disease 2019 (COVID-19) barrier box is being used by health-care workers for protection against aerosol-transmitted infection. Usually, a Macintosh laryngoscope (MC) or a video laryngoscope (VL) is used for endotracheal intubation (ETI). We aimed to determine the most suitable laryngoscope blade in terms of time to ETI, ease of ETI, and the first-pass success rate.
METHODS: American Society of Anesthesiologists Grade I and II patients undergoing surgery under general anesthesia were randomized into the MC and the King Vision VL groups in a 1:1 ratio. ETI was performed using either the MC (the MC group) or the King Vision VL (the VL group) with a COVID-19 barrier box. The first-pass intubation success rate, intubation time, and ease of ETI were analyzed.
RESULTS: The first-pass success rate was higher in the MC group (P = 0.43). The mean duration of ETI was 33 s and 47 s in the MC group and VL group, respectively. The difference was statistically significant between the groups (P = 0.002). The ease of ETI was comparable between the groups (P = 0.57), and the Cormack-Lehane grade was significantly different between the groups (P = 0.0025).
CONCLUSION: ETI duration was shorter in the MC group than in the VL group. Hence, a MC can be used along with a COVID-19 barrier box by experienced operators for the prevention of aerosol spread. Copyright:

INTRODUCTION

Health-care workers (HCWs) are endowed with clinical responsibilities of performing various aerosol-generating procedures such as endotracheal intubation (ETI), insertion of a supraglottic airway device, cardiopulmonary resuscitation, and bronchoscopy.[1]Barrier measures such as a box or a plastic tent are necessary and have been proven effective in reducing the spread of aerosols and the consequent risk.[23456]A coronavirus disease-2019 (COVID-19) barrier box covers the head and neck of a patient. The use of this box has been suggested during ETI, which is one of the most frequent aerosol-generating procedures performed by emergency physicians, anesthesiologists, or critical care HCWs.[7]

However, while using the COVID-19 barrier box in suspected/proven COVID-19 patients, it must be ensured that the intubation time (IT) does not increase and first-pass success rate is not compromised. A Macintosh laryngoscope (MC) or a video laryngoscope (VL) is most frequently used for ETI in many setups. Only a few studies have compared the use of these two tools along with a COVID-19 barrier box. Hence, this randomized controlled trial was planned to study the effect of the COVID-19 barrier box on ETI while using a MC or an AMBU King Vision channeled video laryngoscope (KVVL). The primary objective of our study was to determine the IT. The secondary objectives were to determine the first-pass intubation success rate and perception of ease of ETI. We hypothesized that both devices would be comparable during ETI when used along with a COVID-19 barrier box. The findings of this study might help in selecting the most appropriate laryngoscope while using a COVID-19 barrier box.

METHODS

This study was a prospective, open-label, randomized controlled trial. It was approved by the Institutional Ethics Committee of All India Institute of Medical Sciences, Bhubaneswar (IEC approval No: T/IM-NF/TandEM/20/20 dated May 15, 2020) and registered in the Clinical Trials Registry of India (CTRI/2020/06/025589). Informed consent was obtained from all participants. American Society of Anesthesiologists (ASA) Grade I and II patients of both genders who were aged 18–60 years and posted for elective and emergency surgeries requiring general anesthesia and ETI were included in the study. All the patients had tested negative for COVID-19 in the rapid antigen test or the reverse transcriptase-polymerase chain reaction test (Bio-Rad CFX96, CA, USA). Patients with ASA Grade III and IV, renal failure, crush injury, mental disorders, neurological deficit, known or anticipated difficult intubation, and those with body mass index (BMI) >30 kg/m2 were excluded from the study. Patients with BMI >30 kg/m2 were excluded considering the difficulties in intubation. Moreover, in the conceptual stage, the design of the barrier box had not accounted for accommodation of such patients.[8]After obtaining informed consent from the patients, they were assigned to two groups by using the simple random sampling method in Microsoft Excel for Mac, version 16.48 (Microsoft Corporation, Redmond, WA, USA). The patients were allocated consecutively to either the MC group or the VL group according to the random number sequence.

ETI was performed by anesthesiologists with more than 6 years of experience. Initially, they practiced ETI more than 20 times on mannequins by using a COVID-19 barrier box along with both MC and KVVL. The anesthesiologists put on Level III personal protective equipment (consisting of N95 mask, cap, full-body gown, gloves, shoe covers, and face shield) during ETI. The COVID-19 barrier box was placed covering the head and the neck of each patient. Preoxygenation with 100% oxygen was performed before the induction of general anesthesia through the side opening of the barrier box. All the patients were premedicated with midazolam, ondansetron, and fentanyl injections. General anesthesia was induced with the propofol injection, and ETI was facilitated with succinylcholine.

After ETI, we placed a viral filter on the endotracheal tube and inflated the endotracheal tube cuff to prevent any leakage during positive pressure ventilation and subsequent contamination. The position of the endotracheal tube was confirmed by end-tidal carbon dioxide. A COVID-19 barrier box [Figure 1] with negative suction port[39]was used during the entire procedure starting from preoxygenation. It was removed 30 s after confirming the correct positioning of the endotracheal tube. We defined IT as time from the insertion of the laryngoscope blade into the mouth until the appearance of two capnography waves. The ease of ETI was graded as follows: Grade 1 denoted easy intubation; Grade 2 denoted the need for increased anterior lifting force and pulling of the angle of the mouth by the assistant to augment space; Grade 3 denoted the need for multiple attempts and an intubating stylet; and Grade 4 denoted the failure to intubate with the assigned laryngoscope.[10]Considering an alpha of 0.05 and a power 80% with an allocation ratio of 1:1, a minimum sample size of thirty patients in each group was estimated with an effect size of 0.917.[11]The sample size was calculated using G*Power software for Mac, version 3.1.9.5 (Heinrich-Heine-Universität, Düsseldorf, Germany). Statistical analysis was performed using R, a software environment for statistical computing and graphics (version 3.6.1; the R foundation, Austria, Vienna). Categorical variables are expressed as frequencies or percentages. The data were analyzed for normality by using the Shapiro–Wilk test. A bivariate analysis between categorical variables was performed using the Chi-squared test. Parametric numerical variables are expressed as means, and nonparametric variables are expressed as medians. The bivariate analysis of nonparametric variables was performed using the Wilcoxon rank-sum test by comparing two independent groups, and t-test was used for parametric variables. Statistical significance was set at P < 0.05.

Figure 1

COVID barrier box

RESULTS

Figure 2 shows the CONSORT flowchart of study participants. The preoperative baseline variables and airway assessment parameters were comparable between the groups [Table 1]. The modified Mallampati score differed between the groups, although the difference was not statistically significant (P = 0.6). The distribution of Mallampati grade in both the groups is shown in Figure 3. The outcome variables during laryngoscopy are presented in Table 2. Among the outcome variables, the Cormack–Lehane grade (CLG) was found to differ significantly between the groups (P = 0.0025). The distribution of CLG in both the groups is shown in the bar plot in Figure 4. The VL group had a higher percentage of patients requiring external laryngeal manipulation than the MC group; however, the difference was not statistically significant (P = 0.43). The MC group had a higher first-pass intubation success rate (93%) than the VL group, although the difference was not statistically significant (P = 0.43). The mean IT was 33 s and 47 s in the MC group and VL group, respectively. The difference was statistically significant between the groups (P = 0.002). The distribution of IT is shown in the violin plot in Figure 5. The ease of intubation was comparable between the groups (P = 0.41). The distribution of ease of intubation in both the groups is shown in the bar plot in Figure 6.

Figure 2

Consort flowchart of study participants

Table 1

Baseline variables

Variables	MC (n=30), n (%)	VL (n=30), n (%)	P (CI)
Sex
Male	17 (57)	20 (67)	0.37
Female	13 (43)	10 (33)
Age (years), mean	45.93	43.73	0.54 (−5.04-9.44)
Weight (kg), mean	60.68	58.28	0.32 (−2.43-7.23)
MPG
Class I	7 (23)	13 (43.5)	0.19
Class II	20 (67)	16 (53.5)
Class III	3 (10)	1 (3)

MC: Macintosh laryngoscope, MPG: Mallampati grade, VL: Video laryngoscope, CI: Confidence interval

Figure 3

Distribution of modified Mallampati grade between the two groups

Table 2

Outcome variables during laryngoscopy

Variables	MC (n=30), n (%)	VL (n=30), n (%)	P
CLG
1	8 (26.7)	22 (74)	0.0009*
2	19 (63.3)	8 (26)
3	3 (10)	0
Number of attempts
1	30	28 (94)	0.35
2	0	1 (3)
3	0	1 (3)
ELM
No	23 (76.7)	27 (90)	0.29
Yes	7 (23.3)	3 (10)
Duration of intubation (seconds) Median (IQR	33 (10.25)	47 (24)	0.004*
Ease of intubation
Grade 1	14 (46.7)	18 (60)	0.57
Grade 2	15 (50)	11 (36.7)
Grade 3	1 (3.3)	1 (3.3)
Grade 4	0	0

Wilcoxon rank-sum test, Median (IQR) CLG: Cormack-Lehane grading, ELM: External laryngeal manipulation, MC: Macintosh laryngoscope, VL: Video laryngoscope

Figure 4

Distribution of Cormack–Lehane grade between the two groups

Figure 5

Violin plot showing variation of duration of intubation between the two groups

Figure 6

Distribution of ease of intubation between the two groups

DISCUSSION

In the present study, a significant difference in the IT was observed between the groups. The average IT in the MC group was 33 s, whereas that in the VL group was 47 s. The CLG was significantly better in the VL group. No significant difference was observed in the ease of intubation, first-pass intubation success rate, percentage of patients requiring external laryngeal manipulation, and hemodynamic changes between the groups.

We experienced difficulty in introducing the KVVL while using the COVID-19 barrier box, which may account for the increased IT in the VL group. However, this increase in the IT did not result in decreased oxygen saturation in the VL group. A MC is used more frequently in our setup, which might be another reason for increased IT in the VL group, though we practiced using the KVVL on a mannequin before initiation of the study.

Begley et al. measured the duration of intubation with and without an aerosol box (similar to our COVID-19 barrier box) on a mannequin[12]and found that IT was greater in the presence of aerosol box than in the absence of aerosol box. The authors used a C-MAC VL (Karl Storz) and an intubating bougie in all intubations and reported an IT of 42.9 s without the aerosol box and 52.4 s with the aerosol box. In the present study, the IT in the MC and VL groups was 33 s and 47 s, respectively, even in the presence of the COVID-19 barrier box. We did not use an intubating bougie in any of the patients.

Fong et al. studied the effect of an aerosol box on ETI in both normal and difficult airway scenarios by using a mannequin.[13]They observed that the presence of the aerosol box had no effect on the time to ETI and on the level of difficulty. In the present study, we obtained data regarding the ease of ETI with the COVID-19 barrier box. The ease of ETI could be classified as Grade 1 or Grade 2 in all cases, whereas no instances of Grade 3 or Grade 4 ETI were observed. This finding might be due to the practice on the mannequin before initiation of the study.

Serdinšek et al. conducted a study by using mannequin to compare the IT associated with the use of a VL (C-MAC), a direct laryngoscope, and a supraglottic device with and without the COVID-19 barrier box.[14]They observed that the average prolongation of intubation by using the COVID-19 barrier box was 9 s for the direct laryngoscope and 4 s for the VL. However, in the present study, the IT for the VL with the COVID-19 barrier box was found to be greater, which might be explained by the more frequent use of a direct laryngoscope in our setup.

The present study has some limitations. We did not include patients with difficult airway and those with obesity. Moreover, we did not study the extubation parameters and efficacy of the COVID-19 barrier box in reducing the spread of aerosols to the HCWs. Furthermore, validated measures of baseline health status or comorbidities (e.g. Charlson Comorbidity Index) were not recorded in the present study.

CONCLUSION

The duration of ETI was shorter with a MC blade than with a KVVL when used along with a COVID-19 barrier box in patients with BMI <30 kg/m2. However, KVVL allowed better glottic visualization. Thus, the use of a MC along with a COVID-19 barrier box by experienced operators can be effective in the prevention of aerosol spread. We emphasize that the use of a COVID-19 barrier box would provide extra protection to HCWs. However, it should not be considered a replacement for standard personal protective equipment.

Research quality and ethics statement

The authors of this manuscript declare that this scientific work complies with reporting quality, formatting, and reproducibility guidelines set forth by the EQUATOR Network. The authors also state that this clinical investigation was determined to require institutional ethics committee review, and the corresponding protocol/approval number is T/IM-NF/T and EM/20/20 dated May 15, 2020.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.