|Ahead of print publication
A comparison of direct laryngoscopy versus videolaryngoscopy using aerosol box for intubation in emergency surgeries during Covid-19 pandemic: A pilot study
Deepak Dwivedi1, Parmeet Bhatia1, Manish Aggarwal1, Subrato Sen1, Bhavna Hooda1, Puja Dudeja2
1 Department of Anaesthesia and Critical Care, Command Hospital (Southern Command), Pune, Maharashtra, India
2 Department of Preventive and Social Medicine, Armed College of Medical Sciences, New Delhi, India
|Date of Submission||25-Jul-2020|
|Date of Decision||12-Aug-2020|
|Date of Acceptance||20-Aug-2020|
|Date of Web Publication||09-Sep-2020|
Department of Anaesthesia and Critical Care, Command Hospital (Southern Command), Pune - 411 040, Maharashtra
Source of Support: None, Conflict of Interest: None
Background and Aims: This study was planned to compare intubating conditions with aerosol box, while attempting intubation with either direct laryngoscope (DL) using Macintosh blade or McGrath MAC™, videolaryngoscope (VL). Methodology: Sixty adult patients coming for the emergency surgeries during COVID-19 pandemic were divided equally by consecutive sampling into either Group 1 (DL) or Group 2 (VL). General anesthesia was administered with aerosol box covering the head and trunk of the patient. The laryngoscopy was attempted based on the group allocation with either VL or DL through aerosol box. Following observations were noted, total intubation time, number of attempts, Cormack–Lehane (CL) view, intubation difficulty scale (IDS), use of airway adjuncts, and external laryngeal maneuver. Results: Mean (standard deviation) time taken to intubate was 25.36 (6.22) sec in DL group and 21.9 (5.56) sec in VL group. Median IDS scoring was 1 in DL group and 0 in VL group indicating toward ease of intubation with the videolaryngoscope. Improved glottic view (CL Grade 1) was attained commonly with VL group and higher CL grades (2b) were common with DL group (23.3%). No intubation aids were required in VL group although 30% in DL required bougie for the intubation. External laryngeal maneuver was applied in 40% subjects undergoing DL with no maneuvers needed in VL group. First pass success of intubation was comparable in both the groups. Conclusion: Intubating conditions are favorable with VL when aerosol box is included which requires acquisition of the skills depending on its availability. However, the intubation should be attempted with the technique the clinician has the expertise during this pandemic.
Keywords: Airway management, COVID-19, endotracheal intubation, laryngoscopy, pandemic, personal protective clothing
|How to cite this URL:|
Dwivedi D, Bhatia P, Aggarwal M, Sen S, Hooda B, Dudeja P. A comparison of direct laryngoscopy versus videolaryngoscopy using aerosol box for intubation in emergency surgeries during Covid-19 pandemic: A pilot study. J Mar Med Soc [Epub ahead of print] [cited 2020 Sep 29]. Available from: http://www.marinemedicalsociety.in/preprintarticle.asp?id=294578
| Introduction|| |
COVID-19 pandemic is immensely challenging to health-care workers, more for those involved in aerosol generating procedures such as intubation, extubation, oro-tracheal suctioning, mask ventilation, tracheostomy, and cardiopulmonary resuscitation. Although elective surgeries have been put on hold since the time it was declared pandemic, many patients may present in need of general anesthesia for emergency surgeries. To decrease the risk of exposure to anesthesia provider and staff, various guidelines, and innovations have been suggested recently for safe, accurate and swift management of airway in COVID-19 patients. Although the main routes of transmission of COVID-19 are droplets and close transmission, aerosol transmission is also possible under the condition of long exposure to high concentrations of aerosols in a relatively closed environment. To prevent such transmission inside operating rooms “aerosol box” which consist of transparent plastic cube to cover head and shoulders of patient has been proposed. It has two ports for inserting hands of clinician to facilitate airway management and some modifications have additional port for assistance. This box is suggested, as an additional barrier along with face shield, goggles, and complete personal protective equipment (PPE) to decrease the risk of aerosol transmission.
As the “aerosol box” increases the layer of barriers, simultaneously, it increases the difficulty in airway handling because of poor visibility of glottis and rapid fogging of goggles and face-shield. In addition, there is restriction in hand movements to facilitate the swift and comfortable management of airway, with inherent risk of breach in PPE with tear of gown and up rolling of sleeves during the procedure., Based on the advisory issued by the Indian Society of Anaesthesiologist in April 2020 about the management of the emergency cases during this pandemic, the practice guidelines about intubation suggest, the use of videolaryngoscope for intubation based on its availability as it increases the distance between the operator and patient's head. However, both availability and training or preference of proceduralist with videolaryngoscope differs. A systematic review shows that there is no benefit in reducing intubation attempts and time required for intubation with videolaryngoscope compared to conventional direct laryngoscopy while managing the airway without an aerosol box.
This present study was, therefore, envisaged as one cannot completely underplay the role of direct laryngoscopy over videolaryngoscopy without a scientific evidence. Our study aimed at comparing the intubating conditions in terms of first attempt success of intubation, time required for intubation, and intubation difficulty scale (IDS) scoring with aerosol box placed in between the anesthesiologist and the patient while attempting direct laryngoscopy/videolaryngoscopy during the emergency surgeries.
| Methodology|| |
This pilot study was planned after obtaining the ethical clearance from the institution ethics committee. All patients presenting for the emergency surgeries in view of the cancellation of the elective surgeries during this pandemic under general anesthesia were included and consecutive sampling was done where the first 30 patients were included in Group 1, direct laryngoscope (DL) and the next 30 successive patients were included in Group 2, videolaryngoscope (VL). The basis of group division was the method of laryngoscopy employed for the airway management of these patients. The exclusion criteria included, age <18 years, cervical spondylosis, restricted neck mobility, diabetes, severe obesity, rheumatoid arthritis, thyromental distance of <6 cm, and failure of intubation by DL. All patients were explained and demonstrated the use of aerosol box preoperatively and written informed consent was obtained.
All patients on arrival in operation theater (OT) whether tested prior or not, were considered as COVID suspect and all standard precautions were taken during the aerosol generating procedures such as intubation with confirmed fasting. Patients were connected with the standard monitoring and an intravenous (IV) access was obtained. The head of the patient was made to rest on the gel ring to maintain the head position, following which the aerosol box was placed over the head end of the patient [Figure 1]a. Dimensions and specifications of aerosol box used were the same as originally designed by Tseng and Lai of Taiwan. After donning the full protective clothing including the face shield by the anesthesiologist, the preoxygenation was done with the tight-fitting mask [Figure 1]a. The induction was done with injection propofol 2 mg/kg, fentanyl 1.5 μg/kg and rapid sequence intubation without cricoid pressure was done at 60 s after the administration of the injection succinylcholine 2 mg/kg IV. Laryngoscopy was attempted with either standard Macintosh laryngoscope or McGrath MAC™ (Medtronic, India) videolaryngoscope based on the group selection by a most experienced anesthesiologist [Figure 1]b. The following parameters were noted which included, time to intubate in seconds, number of attempts, Cormack Lehane (CL) view, IDS, any airway adjuncts, or external laryngeal maneuver used during the intubation. Time to intubate was defined from the duration the laryngoscope blade is inserted till the endotracheal tube is passed through the glottis and with the confirmed trace on the capnograph. A progressive objective assessment with IDS scoring entails seven parameters for the quantitative assessment of the complex intubating conditions. The parameters assessed are number of attempts and operators, alternative techniques, CL Grade, lifting force, laryngeal pressure, and vocal cord mobility. IDS score of 0 is considered easy, 1–5 score is rated as slightly difficult and more than 5 is considered a moderately difficult airway to major difficulty.
|Figure 1: (a) Preoxygenation with tight fitting mask through “Aerosol Box.” (b) Improved glottic view achieved with Mc Grath MAC™ videolaryngoscope for intubation through “Aerosol Box”|
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Statistical analysis was done using the software, SPSS version 22 (SPSS Inc., Chicago IL, USA). Quantitative data between the two groups were compared using the Student's t-test. The discrete data are represented as mean (standard deviation) and the ordinal data were calculated as median with interquartile range. The significance of median between the two groups was compared using two tailed Mood's median test. The proportion between the groups was analyzed with Z score calculator and “N-1” Chi-square test.
| Results|| |
A total of 60 patients were included in the study after meeting the inclusion criteria. The type of surgeries for which the intubations were carried out in two groups are presented in [Table 1]. Comparison of demographic data in both the groups is shown in [Table 2].
|Table 1: Type of emergency surgeries in two groups for which intubations were done|
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|Table 2: Comparison of demographic and the American Society of Anesthesiologists profile of two groups|
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Intubation characteristics were compared between the two groups, where the intubation time measured for Group 1 (DL) was 25.36 ± 6.22 s and was significantly shorter (21.9 ± 5.56 s) with the use of VL in Group 2 [Table 3]. Median IDS score between the two groups were comparable [Table 3]. IDS score was uniformly distributed without any outliers as represented in the Box Plot figure [Figure 2]. Higher CL grade (2 b) was observed more with the DL group [Table 3]. Group 1 also required intubation aids and external laryngeal maneuver when compared with the videolaryngoscopy group and the results were statistically significant [Table 4]. The intubation was done in the first attempt in majority of the cases in Group 1 and in all in Group 2 and the results were statistically insignificant [Table 4].
|Table 3: Comparison of Intubation time and Cormack– Lehane grades with intubation difficulty scale scores in two groups|
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|Figure 2: Comparison of intubation difficulty scale scores in two groups Box and Whisker Plot: (a) The direct laryngoscopy group. (b) The videolaryngoscopy group|
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| Discussion|| |
Inclusion of aerosol box during intubation as an innovative and a barrier measure along with regular use of full PPE including impermeable gown, face shield, goggles, and double gloves tend to decrease spread of aerosols to the anesthesiologist and other OT staff. There are various modifications of intubation box, originally designed by Tseng and Lai of Taiwan. New generation box include additional holes for bougie insertion and suction port for creating negative pressure. Vijayaraghavan and Puthenveettil modified the dimensions of the box along with the shape and the location of inserting ports as per their study on mannequin. Kloka et al. have designed an aerosol protection dome using packaging tray material used in bypass machine utilized for cardiac surgeries. In the present study, aerosol box used was the same in dimensions and specifications as designed by Tseng and Lai of Taiwan and used by Canelli et al. to analyze aerosol spread in simulation, which proved to be an additional protection along with PPE.,
Aerosol box is fraught with innate challenges. Head of the patient positioned over the pillow could not provide a stable position due to the interface between the patient's head and the anesthesiologist. In our study, we have used gel rings for positioning the head and maintained it successfully throughout the intubation. In addition, to this we also placed folded towels to accommodate the edges of aerosol box and its foot end with drapes to reduce the spread of aerosol caudally as was suggested by Singh et al. in their study.
Several other factors are known to cause intubation difficulty using aerosol box like, restriction in hand movements to facilitate airway positioning and mask holding, and poor glottic view due to multiple barriers with fogging of goggles., Similar difficulties were observed initially in our center too, but we improved with simultaneous practice on mannequin resulting in better ergonomics and successful attempts to intubation.
Recent guidelines preferred videolaryngoscopy over conventional direct laryngoscopy in view of increased first pass chances of intubation with the complete avoidance of close contact to patient's airway.,, Although literature on comparison of videolaryngoscope with Macintosh laryngoscope during adult intubation suggest, either there is no increase or rather decrease in first attempt intubation., While in contrast, there is a greater first pass success rate and improved glottic visualization in outside operating room scenario among less experienced clinicians with the use of VL when compared to DL. The results were contrary in the same study with the experienced clinicians when both VL and DL were compared. In our study, first pass intubation success was 100% and 90% for VL and DL respectively in the hands of an experienced anesthesiologists [Table 4].
The study reported improved glottic view in majority (70%) of the subjects having CL Grade 1 in VL group when was compared with DL group [Table 3]. The observations are in accordance with the Cochrane review done by Lewis et al. where VL was found to minimize the difficult glottic view. Similar improvement in CL grade with VL was observed during out of hospital cardiopulmonary resuscitation. In addition to the ergonomics involved while doing the intubation through the aerosol box we also observed that while attempting intubation with DL, there was a hindrance due to altered intensity and brightness of Macintosh laryngoscope light reflecting from the various interface such as aerosol box, face shield, and goggles.
Intubation aids including stylet and bougie, are considered integral part of difficult airway cart in COVID-19 patients and as per Difficult Airway Society guidelines, preferably the endotracheal tube must be loaded with a bougie or it should be readily available in the vicinity while using Macintosh laryngoscope. In present study, nine (30%) cases in DL group required adjuncts; like bougie and 11 (40%) cases required assistance in the form of external laryngeal manipulation to facilitate intubation. The results were clinically as well as statistically significant, when they were compared to VL group [Table 4]. VL minimizes the chances of aerosol spread caudally from the aerosol box with minimal assistance required in terms of the adjuncts as well as external laryngeal pressure. Kojima et al. have used a modified enclosure device to achieve airtight conditions, which allows assisting staff to access through barrier without exposure to aerosols.
The IDS scoring, as a marker of difficulty faced during intubation was used in this study. It takes into account both objective and subjective criteria, which evaluates intubation difficulty including CL grade. Overall IDS score was not more than five in any of the patient in both groups, although in DL group, fifteen patients had IDS score in range of 1–5 (slight difficulty) while in VL group only nine patients had IDS score of 1 (slight difficulty). Similarly, Loughnan et al. compared performance of DL and VL in terms of IDS, found higher score in DL but the results were not statistically significant as was evident in our case. Kim et al. compared the two intubation modalities in children, and found significantly higher IDS score in direct laryngoscopy. Jafra et al. also concluded that the ease of endotracheal intubation was better with Glidescope videolaryngoscope when compared with DL having the higher IDS scores.
Cochrane systematic review by Lewis et al. showed no difference in the intubation time between the VL and DL and they attributed it to the heterogeneous data related to the varied definition of the time to intubate which was obviated from the meta-analysis. However, time to intubation was shorter with VL than DL during nasotracheal intubation and in obese subjects in various studies., The intubation time when compared between the two groups in our study was statistically significant with DL group taking more time for intubation.[Table 3] This could be perhaps related to the manual dexterity issues with the use of DL with inclusion of aerosol box for intubation and increased interfaces making the airway iatrogenically difficult and hence, increasing the time to intubate.
The strength of this study is to provide the insight into the intubating conditions when it is compared between the preferred modality (videolaryngoscope) and the most widely used direct laryngoscopy for intubation during the pandemic.
Being a pilot study is a limitation, but it can act as a prelude to conduct randomized controlled trials with collation of data from the multiple center, which will aid in substantiating its results for providing the safer airway management which will benefit both, the patient as well as the health-care provider.
| Conclusion|| |
COVID-19 pandemic situation made the use of aerosol box as an effective and definitive barrier measure during airway management to prevent the operator and OT staff from aerosol transmission. At the same time, difficulty arise in handling airway, which may be handled better with the familiar technique of intubation with either DL or VL depending on the expertise and the availability. VL is although preferred and advocated as it improves the glottic view, with shorter intubation time with lesser use of adjuncts, external laryngeal manipulation and lower IDS score.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]