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Table of Contents
ORIGINAL ARTICLE
Year : 2021  |  Volume : 5  |  Issue : 2  |  Page : 88-92

Plastic screen versus aerosol box as a barrier during endotracheal intubation: A simulation-based crossover study


Department of Anaesthesiology, Institute of Liver and Biliary Sciences, New Delhi, India

Date of Submission11-Nov-2020
Date of Decision02-Jan-2021
Date of Acceptance06-Jan-2021
Date of Web Publication16-Apr-2021

Correspondence Address:
Dr. Amal Francis Sam
Department of Anaesthesiology, Institute of Liver and Biliary Sciences, Vasant Kunj, New Delhi - 110 070
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/bjoa.bjoa_241_20

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  Abstract 


Background: The severe acute respiratory syndrome coronavirus-2-2019 pandemic has posed significant challenges and barrier devices such as aerosol/intubation box, intubation tent, and intubation screen have been widely used during endotracheal intubation by the clinicians without any definite proven benefit. The initial experience at our institute with the intubation box posed some difficulties leading to failed intubations. Hence, as an alternative, we switched to a transparent plastic intubation screen that is likely to provide better vision and space during intubation. We evaluated the impact of intubation box and plastic screen on intubations in this simulation-based crossover study. Materials and Methods: Ten anesthesiologists performed 90 intubations in an operating room on a Laerdal® adult airway management trainer. Each participant performed 9 intubations, 3 without any barrier and 3 each with intubation box and plastic screen. The primary outcome was intubation time; secondary outcomes included first-pass success and breaches to personal protective equipment. Results: Intubation time with no barrier was significantly shorter than with the intubation box (median interquartile range [IQR]: 25 [22–28] vs. 40 [30–51] s, P < 0.001) and with the screen (median [IQR] 29 [25–35] s, P = 0.015). The intubation time was significantly lesser with the screen compared to the box (P = 0.023). The first-pass success was 86.66%, 96.66%, and 100% in the box, screen, and no barrier groups, respectively. Conclusion: In comparison to an intubation box, the transparent plastic screen decreases intubation times and has greater operator comfort. These devices require further evaluation for patient safety.

Keywords: Aerosol, airway, barrier, COVID-19, intubation, plastic screen


How to cite this article:
Ponnappan KT, Dhingra U, Yadav AY, Sam AF. Plastic screen versus aerosol box as a barrier during endotracheal intubation: A simulation-based crossover study. Bali J Anaesthesiol 2021;5:88-92

How to cite this URL:
Ponnappan KT, Dhingra U, Yadav AY, Sam AF. Plastic screen versus aerosol box as a barrier during endotracheal intubation: A simulation-based crossover study. Bali J Anaesthesiol [serial online] 2021 [cited 2021 Jun 23];5:88-92. Available from: https://www.bjoaonline.com/text.asp?2021/5/2/88/313892




  Introduction Top


The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-2019 pandemic has posed significant challenges to the health-care workers (HCW) due to the risk of viral transmission. The incidence of SARS-CoV-2 among HCW is about 5% of those involved in the care of infected patients.[1] Based on our current understanding, the SARS-CoV-2 is transmitted mainly through droplet or respiratory secretions,[2] with emerging evidence of airborne transmission.[3]

There is a high risk of viral transmission to the anesthesiologist during tracheal intubation and extubation. Exhaled air dispersion is possible up to 15–25 cm from the leak between bag and mask interface and up to 40–50 cm during coughing and gagging.[4] Despite the use of personal protective equipment (PPE), there have been reports of HCW getting infected with SARS-CoV-2.[5],[6] This has led to many innovations, mainly in the form of barriers during tracheal intubation.

Barrier devices such as aerosol/intubation box, intubation tent, and intubation screen have been widely used among clinicians without proven efficacy and safety. In addition, widespread promotion of these devices on webinars and social media has led to an increased use of these devices, at times compromising the patient safety due to failed intubations.[7] One of the devices that became popular during these times is the intubation/aerosol box, which is a transparent plastic cube that covers the patient's head and shoulders.[8]

The initial experience at our institute with the intubation box posed some difficulties leading to failed intubations. Restricted hand movement was considered the main reason for these difficulties. Simpson et al. reported the use of a plastic screen suspended vertically as a barrier between the patient and the anesthesiologist as superior to the aerosol box and comparable with no barrier in particle exposure measured with an airborne particle counter.[9] Hence, as an alternative, we switched to a transparent intubation screen that is likely to provide better vision and space during intubation. The present study is a comparison of the two barrier techniques (box vs. screen) in a simulated atmosphere.


  Materials and Methods Top


The study was performed in an operating room on a Laerdal® adult airway management trainer on the operating table. The study was exempted from the ethical review board since it was performed on a manikin. A silicone head ring or pillow was used to provide adequate flexion of the neck. All the intubations were performed by direct laryngoscopy with a malleable stylet. Although the use of a video laryngoscope is preferred, we chose to conduct the present study using a conventional direct laryngoscope to closely mimic the scenarios in a developing nation where video laryngoscopes are not widely available.

The size of the laryngoscope blade was based on the operator's preference. A 7.5 mm cuffed endotracheal tube was used for all the intubations. Intubations were performed as per the rapid sequence induction (RSI) technique. Intubation box or the aerosol box used in the study was prepared by the biomedical personnel of our institution. The dimensions of the box were 50 cm × 50 cm × 40 cm [Figure 1]. The armholes were 10 cm in diameter. The transparent plastic screen that was used as a barrier was 200 cm × 180 cm with armholes of 10 cm in diameter [Figure 2].
Figure 1: Dimensions of intubation/aerosol box

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Figure 2: Dimensions of plastic screen

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Ten anesthesiologists participated in this study. Each participant performed 9 intubations: 3 without any barrier and 3 each with intubation box and plastic screen, resulting in a total of 90 intubations. On each day, 30 intubations were performed by the 10 operators, one intubation of each technique by each operator. The operator performed the intubations in sequence, operator 1–10 serially. However, the barrier technique was decided by computer-generated randomization (www.randomizer.org). This was repeated on days 2 and 3 and a total of 90 intubations were performed. The simulated process of intubation was in compliance with the Difficult Airway Society guidelines.[9] All the participants were wearing PPE, which included an impervious sterile gown, double gloves, shoe cover, N-95 mask, head cover, and a face shield. Participants were oriented to the simulation environment and information was provided regarding the intubation box and plastic screen.

The intubation box was placed over the manikin so that it covered the entire head, and the proximal surface of the box (one with the holes) was about 10 cm away from the head of the manikin. The anesthesia circuit and mask were introduced from the open end of the box. The anesthesia provider inserted the hands into the box through the armholes provided. The plastic screen was placed at the head end of the operating table. The two top ends of the screen were clipped to two drip stands placed on either side of the table to hold the screen with the lower end just touching the floor. The anesthesia circuit and mask were introduced from the right side of the drip stand. The holes for the arms were made separately at a level to suit each operator [Figure 3].
Figure 3: Intubation using a plastic transparent screen

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For all intubations, the laryngoscope was placed on the left and the styletted endotracheal tube on the right side of the manikin. At any time, the participant could request for adjustment of the height of the table. After preoxygenation, administration of induction agents and neuromuscular blocking drugs was simulated according to the RSI technique. Intubation was performed 60 s after administration of the neuromuscular blocking agent. Participants were free to choose their rescue techniques with the equipment provided. Intubation was considered as failed if it took more than 2 min after removal of the facemask. A second attempt was performed soon after the failed first attempt without mask ventilation. Successful intubation was confirmed by observing the lung expansion. The intubation time was defined as the time from removal of face mask to delivery of the first breath via the endotracheal tube.

A single experienced anesthetic technician, who was not a part of the study, assisted all the intubations (for providing rescue devices and pilot balloon inflation). An anesthesia trainee who was not a part of the study was assigned to note the timing of each intubation. After each intubation, the participant was asked to record the comfort score on a scale of 1–10, with 10 being most comfortable. Qualitative feedback was obtained about the reasons for discomfort. The operator was then assessed by visual inspection for any breach in the PPE. Any compromise in the PPE exposing the operators' skin was considered a breach in our study. Our primary outcome was the time taken to intubate. Secondary outcomes were first-pass intubation success, breaches in PPE, comfort score, and causes of discomforts.

All continuous variables were represented as median and interquartile range (IQR). The primary outcome was tested using a Kruskal–Wallis test with Bonferroni's correction. Other continuous variables were compared using Mann–Whitney U-test and proportions were compared using Fisher's exact probability test. Correlation between two continuous variables was tested using spearman's correlation coefficient. P < 0.05 was considered significant.


  Results Top


The ten participants (8 men and 2 women) had a median age of 31 years (IQR: 30–33) and a median experience 3.5 years (IQR: 1–5.5). Intubation time with no barrier was significantly shorter than with the intubation box (median [IQR]: 25 [22–28] vs. 40 [30–51] s, P < 0.001) and with the screen (median [IQR]: 29 [25–35] s, P = 0.015) [Table 1] and [Figure 4]. The intubation time was significantly less with the screen compared to box (P = 0.023). The firs- pass success was 86.66%, 96.66%, and 100% in the box, screen, and no barrier groups, respectively. Age correlated poorly with time taken to intubate with the box (rs = −0.15, P = 0.43), with the screen (rs = −0.06, P = 0.75), and without any barrier (rs = −0.23, P = 0.22). Years of experience also correlated poorly with time taken to intubate with the box (rs = 0.06, P = 0.73), with the screen (rs = 0.06, P = 0.75), and without barrier (rs = −0.26, P = 0.16).
Table 1: Outcomes with intubation box, screen, and without barrier

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Figure 4: Comparison of time to intubate, in three groups

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The freeform commentary regarding the discomfort revealed that stylet hitting top of the box was the most common cause of discomfort. Various discomforts faced by the operators and their frequency are displayed in [Figure 5]. In the 90 intubations, we received 42 freeform commentaries. In intubation box, stylet hitting the top of the box was the most common discomfort. In the screen group, an impaired vision was the only discomfort reported by the operators. There was one breach in PPE in the group using the intubation box where the sleeve got rolled up above the glove and exposed the wrist area of the operator.
Figure 5: Difficulties faced with the barrier method

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  Discussion Top


The main findings of our study include longer intubation time when participants used the intubation box. The first-pass success was accomplished by all participants when no barrier was used. However, one participant in the screen group and four participants in the box group needed a second attempt for successful intubation. Participants while using the intubation box reported lesser comfort scores in comparison with the other methods. To protect the HCW from acquiring infection during aerosol-generating procedures such as endotracheal intubation, novel aerosol boxes were developed, but studies have shown that they compromise both efficacy and safety.[10] As an alternative, a transparent plastic screen is likely to improve the operator's comfort. In a study, a Lighthouse 3016IAQ airborne particle counter (Fremont, CA) was used at the level of operator and different barrier techniques were compared with “no barrier” technique. In this study, the sizes of airborne particles were between 0.3 and 5 μ, the intubation box was associated with increased exposure of the operator to the aerosol. In the same study, the protection offered by a vertical transparent plastic sheet was significant till 30 min and as the time elapsed, exposure of the operator was similar when compared to “no barrier” technique. A sealed aerosol box with a wall suction connected through a heat/moisture exchange viral filter performed better till 360 min regarding protection from the aerosol.[9]

To our knowledge, this is the first formal study that aimed to look at the operator comfort and successful intubations using a simple plastic screen and compare it with the intubation box. The present study showed that the aerosol box significantly increased the intubation time. The greater the intubation time, the greater is the operator exposure to aerosol as well as the risk of hypoxia to the patient leading to increased morbidity and mortality.[11]

The most common reason leading to difficulty in intubation with the box was the stylet hitting the top of the box. The dimensions of the intubation box can make the use of a stylet tricky and the use of a bougie quite difficult. Most operators (26.66%) reported the stylet striking the roof of the box, impeding movement. The major area where the screen scores over the box is that there is less difficulty in manipulations, maneuvers, and hand movements. Airway operators often make fine movements and manipulations to achieve the optimal view, which may not be possible with the box. Good optics is crucial to visualization of the vocal cords, and this was impeded considerably by both the box (26.66%) and the screen (23.33%). This not only influences the intubation time but also decreases the chances of first-pass success in both the box and screen groups.

A universal cause of discomfort in all three groups was the fogging of the face shield. It is possible that in a real-life scenario, airway operators may be compelled to remove the face shield in a difficult airway situation. This puts the operator at an exceptional risk of exposure, thereby highlighting the importance of using an additional barrier (screen or box). Proper seal of the N95 mask should be ensured prior to donning of PPE to avoid fogging. Simple antifog measures are described by authors in China, but considering the gravity, a simulation study may be warranted in the future with this specific outcome.[12]

There was a single breach in PPE where the gown sleeve got rolled up to expose the wrist. Similar breaches were identified by Begley et al., and this is a serious, although rare safety concerns.[10] It may be useful to tape the glove at the wrist. The lower comfort scores with the intubation box show that while adding a layer of safety, there is a considerable loss of operator comfort. In our study, we did not find any strong correlation between age and years of experience with time taken to intubate. However, the present study is too small to draw any definite conclusions.

Modifications to the intubation box have been attempted, but the new boxes will again need robust studies to validate clinical use.[13] Considering the rapid need for simple protective equipment, the plastic screen may offer similar protection as offered by the intubation box while providing a better comfort level to the operator. The use of plastic drapes designed by Brown et al. has been described, but its complex assembly which is labor intensive may not be widely practiced.[14] An ideal aerosol barrier technique should be relatively simple, allows good visibility, free arm movements, with an adequate seal, and poses no contamination risk either during or after its use, and such a method is yet to be established, to our knowledge.[15]

The vertical plastic sheet barrier has performed better than the intubation box with respect to exposure of the operator to the airborne particles.[9] However, the function of the box or the plastic screen is mainly to isolate the aerosols that will have to be eventually sucked by the application of negative suction to make it effective. Additional application of negative pressure suction at the patient end may minimize the aerosol exposure to the operator and decrease aerosols.[16],[17] Further studies are required to evaluate the combination of vertical screen and negative suction. The major limitation of our study is that we did not test the efficacy of the screen against airborne transmission. Another drawback is the limited sample size in testing the secondary outcomes. Although the intubations were performed in a simulated environment, they may still not adequately replicate a real-life scenario. Variations in patient body habitus, comorbidities, type of equipment, and personnel are unaccounted for. Till confirmatory trials are available, the use of appropriate PPE remains mandatory, before attempting to add either the screen or box in airway management.


  Conclusion Top


In comparison to an intubation box, the transparent plastic screen decreases intubation times and has greater operator comfort. These devices require further evaluation for patient safety and actual protection provided by each of them.

Acknowledgments

The authors acknowledge all the residents of the department of anesthesiology, ILBS – New Delhi, for performing the intubations.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Sikkema RS, Pas SD, Nieuwenhuijse DF, O'Toole Á, Verweij J, van der Linden A, et al. COVID-19 in health-care workers in three hospitals in the south of the Netherlands: A cross-sectional study. Lancet Infect Dis 2020;3099:1-8.  Back to cited text no. 1
    
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World Health Organization. Modes of transmission of virus causing COVID-19: implications for IPC precaution recommendations: scientific brief. World Health Organization; 2020. Available from venturesafrica.com/apostories/modes-of-transmission-of-virus-causing-covid-19-implications-for-ipc-precaution-recommendations/. [Last accessed on 2020 Mar 27].  Back to cited text no. 2
    
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(NCIRD) NC for I and RD. Interim infection prevention and control recommendations for healthcare personnel during the coronavirus disease 2019 (COVID-19) pandemic. Cent Dis Control Prev 2020;2:1-11.  Back to cited text no. 3
    
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Chan MT, Chow BK, Lo T, Ko FW, Ng SS, Gin T, et al. Exhaled air dispersion during bag-mask ventilation and sputum suctioning – Implications for infection control. Sci Rep 2018;8:1-8.  Back to cited text no. 4
    
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Meng L, Qiu H, Wan L, Ai Y, Xue Z, Guo Q, et al. Intubation and ventilation amid the COVID-19 outbreak: Wuhan's experience. Anesthesiology 2020;132:1317-32.  Back to cited text no. 5
    
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Tseng JY, Lai HY. Protecting against COVID-19 aerosol infection during intubation. J Chin Med Assoc 2020;83:582.  Back to cited text no. 8
    
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Simpson JP, Wong DN, Verco L, Carter R, Dzidowski M, Chan PY. Measurement of airborne particle exposure during simulated tracheal intubation using various proposed aerosol containment devices during the COVID-19 pandemic. Anaesthesia 2020;75:1587-95.  Back to cited text no. 9
    
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Begley JL, Lavery KE, Nickson CP, Brewster DJ. The aerosol box for intubation in COVID-19 patients: An in-situ simulation crossover study. Anaesthesia 2020;75:1014-21.  Back to cited text no. 10
    
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Yao W, Wang T, Jiang B, Gao F, Wang L, Zheng H, et al. Emergency tracheal intubation in 202 patients with COVID-19 in Wuhan, China: Lessons learnt and international expert recommendations. Br J Anaesth 2020;125:1-8.  Back to cited text no. 12
    
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Canelli R, Connor CW, Gonzalez M, Nozari A, Ortega R. Barrier enclosure during endotracheal intubation. N Engl J Med 2020;382:1957-8.  Back to cited text no. 13
    
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Brown H, Preston D, Bhoja R. Thinking outside the box: A low-cost and pragmatic alternative to aerosol boxes for endotracheal intubation of COVID-19 patients. Anesthesiology 2020;133:7-8.  Back to cited text no. 14
    
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Thiruvenkatarajan V, Wong DT, Kothandan H, Sekhar V, Adhikary SD, Currie J, et al. Airway management in the operating room and interventional suites in known or suspected COVID-19 adult patients: A practical review. Anesth Analg 2020;131:677-89.  Back to cited text no. 15
    
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