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Intubation strategy in COVID-19 era: An observational study

 Department of Anesthesia, Max Institute of Laparoscopy, Endoscopy and Bariatric Surgery, Max Super Speciality Hospital, New Delhi, India

Date of Submission08-Jan-2022
Date of Acceptance16-Feb-2022
Date of Web Publication08-Jul-2022

Correspondence Address:
Aparna Sinha,
Max Institute of Laparoscopy, Endoscopy and Bariatric Surgery, Max Super Speciality Hospital, Saket, New Delhi - 110 017
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jmas.jmas_11_22

PMID: 35915524


Background and Aims: Aerosol protection equipment aim at protecting the anaesthesiologist, from aerosol-borne infections, namely, severe acute respiratory syndrome corona virus-2.
Methods: We improvised the first-generation intubation box (IB) by increasing its dimensions, including heat and moisture exchanger with filter, suction catheter, and attaching arm sleeves to make a modified intubation box (MIB). The impact of IB, MIB and transparent sheets (TS) on the patient outcomes during airway management was evaluated.
Results: A significant difference in median (interquartile range in minutes) was observed in time to intubate between IB (4 [4–5]); TS (0.5 [0.3–0.5]) and MIB (0.3 [0.3–1.5]): P = 0.004); and airway devices; McCoy (0.5 [0.3–2]), CMac (0.5 [0.3–1.5]): P = 0.004. First-pass success was 100% with the TS, whereas more than three attempts were required with IB 66.7% and 5.2% with MIB. Video laryngoscope was associated with less airway-related adverse events (ARAEs). The need for mask ventilation (and hence possible aerosolisation) was maximum with IB. All the ARAEs resolved uneventfully. No breach of personal protective equipment was observed; none of the health-care professionals involved in patient care developed any symptoms suggestive of COVID-19.
Conclusion: Video laryngoscope is favourable for managing airway in COVID-19 times. In view of the ongoing pandemic and added protection that it offers, it is worthwhile to include the MIB in the armamentarium for managing the airway of patients with COVID-19.

Keywords: Aerosolisation, anaesthesia, box, COVID-19, intubation

How to cite this URL:
Sinha A, Punhani D, Sharma A, Dhakate KG, Garg N, Patro S. Intubation strategy in COVID-19 era: An observational study. J Min Access Surg [Epub ahead of print] [cited 2022 Aug 14]. Available from:

  Introduction Top

As we reboot the health-care facilities for increasing the non-COVID-19 work, it becomes imperative to protect the operation theatre (OT) environment during airway management owing to its aerosol-generating potential. It is vital to plan out how the health-care professionals (HCPs) can protect themselves and the operating room environment in the process of anaesthesia and perioperative care. Aerosol protection equipment (APEs) are barriers to protect HCPs from infection with severe acute respiratory syndrome corona virus-2, during aerosol-generating procedures. Aerosol box is one such innovation; it is a transparent box that forms a barrier between the patient and the anaesthesiologist. The aerosol box (also referred to as intubation box [IB]), made of acrylic was developed to serve as a protective shield between a possible patient with COVID-19 and the care providers at the time of airway management and intubation. This was further intended to minimise the contamination of the OT environment. The aerosol/IB is undergoing transition and has been improvised by several practitioners since its first introduction by Lai Hsien-Yung.[1]

We tested aerosol protection techniques, namely, IB, the transparent sheets (TS) and the modified intubation box (MIB) to assess the patient outcomes and difficulties if any. We started with the initial IB; however, due to concerns of the leak around the armholes and the ergonomics of the IB, we suggested some modifications to the local vendor. The same was referred to as the MIB. Based on suggestions and lessons from previously published literature, our MIB was modified to allow bougie insertion and had a port for connecting the HME filter with suction. We further modified the box by attaching sleeves to make it somewhat airtight and to prevent spillage of aerosols towards the anaesthesiologist and HCPs around [Figure 1]a and [Figure 1]b. Although the MIB was being prepared, we used TS as depicted in [Figure 2]. After its availability, all participants used only MIB to secure the airway device. To consider any device or technique as a part of the armamentarium, it must be assessed for efficacy and safety; hence, we compared the outcomes from all the techniques.
Figure 1: (a) Picture depicting specifications of the modified intubation box (this was studied). One can appreciate holes with sleeves to facilitate arm movement of the anaesthesiologist while forming a barrier and the hole on the right side for the first assistant. (b) Depicts two holes with swivel on the ceiling of the modified intubation box. The heat and moisture exchanger with filter with suction can be connected to one of them, to ensure aerosols generated during airway management can be sucked out. The other hole is opened only for bougie insertion, in case there is any requirement

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Figure 2: This depicts the usage of transparent sheets to cover the head end of the patient while securing airway in patients suspected of severe acute respiratory syndrome corona virus-2 infection

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  Methods Top

With the approval of the Institutional ethics committee of our hospital (RS/MSSH/DDF/SKT-2 IEC/ANARES 20-5) and written informed consent of our patients, we analysed the outcomes and challenges from different intubation techniques adopted in patients posted for surgery under general anaesthesia at our health-care facility. Adult patients American Society of Anaesthesiologists I, II, III, age between 18 and 80 years were enrolled for surgery between May 2020 and July 2020 were included in the study. Reverse transcription-polymerase chain reaction (RTPCR) positive, patients with any symptoms suggestive of COVID disease and any obvious difficult airway were excluded. All surgeries were performed in the designated COVID-19 facility and all operation theatres were negative pressure OTs.[2],[3]

As per institutional COVID-19 protocol, at the time of admission to non-COVID-19-related surgery, all patients were COVID-19 negative for RT-PCR, the sample taken in preceding 72 h. However, assuming the test to be 20% false negative, we considered them all as RT-PCR positive. There were some patients who had to be accepted for surgical intervention without their COVID status, in view of surgical emergency. Before the first patient in middle of lockdown, all anaesthesiologists were familiarised with the perioperative protocols using regular webinars and online meetings. Each participant was made to perform at least four intubations using the box on the manikin. All participants were familiarised with the techniques used and the guidelines that were followed. Our team consisted of six anaesthesiologists with experience of more than 10 years; they were familiarised with difficult airway Society (DAS) and All India Difficult Airway Association (AIDAA) guidelines. IB,[1] TS, and locally MIB as aerosol protection techniques [Figure 1] were used for all patients. Data were collected by an operating room technician, not involved in the study. The choice of laryngoscope (between MacCoy and CMac; D blade size 4) was as per the decision and judgement of the anaesthesiologist performing intubation. The choice of the laryngoscopes was to avert any possible difficult intubation, that could be preempted.[4] Data were collected from the electronic health record of the hospital.

The airway management technique we followed was in compliance with the DAS and AIDAA COVID-19 guidelines.[2],[3],[4]

In the OT the steps of taking up the patient and airway management were revisited. For performing anaesthesia, two anaesthesiologists were allocated along with an experienced operating room technical team. The roles of each person present in the OT were clearly defined. The anaesthesiologists wore personal protective equipment consisting of a face shield, spectacles or goggles, mask (N95), gowns with a plastic apron and two gloves, as per World Health Organisation guidelines.

Patients were advised betadine 0.23% gargles in their room and were ensured to be wearing a 3 ply surgical mask while being wheeled into the pre-operative holding area. Intravenous access was ensured in the pre-operative area and glycopyrrolate 0.2 mg and 1 mg midazolam were administered intravenously. Twin nasal cannula was placed underneath the surgical mask. Preoxygenation using 5 L oxygen in 30-degree head up was initiated in the OT, with mask in situ.[4] On receiving the patient in the OT, standard monitors were established and 25 mg ketamine and fentanyl 1–2 mcg/kg (ideal body weight) were administered intravenously. After ensuring that the patient was calm and sedated the aerosol protection box was placed over the upper torso, as depicted in [Figure 3]. Oxygen 5 L continued till this point. The placement of the HME filter and a suction to the hole in the ceiling of the MIB was ensured. Anaesthesiologist took a position at the head end, and ensured correct placement of all monitors and secured his/her arm into the sleeves of the aerosol protection box. Oxygen through the twin nasal cannula was discontinued, the surgical mask was removed from the face of the patient, face mask was applied and induction was initiated using propofol 1–2 mg/kg. As per the AIDAA COVID 19 guidelines we have to use rapid sequence intubation during COVID-19 times, to minimise the duration of mask ventilation and possible aerosolisation. However, we preferred precurarisation. Atracurium besylate 5 mg IV was used to precurarise at this point. Soon after administering the induction dose of propofol, full dosage of atracurium besylate was administered and laryngoscopy was attempted within 1 min of precurarisation.
Figure 3: (a) Incidence of severe adverse events with respect to laryngoscope used. It shows that the airway-related adverse event was comparable between the devices. (b) Incidence of severe adverse events with respect to aerosol protection equipment. It shows that in modified intubation box and transparent sheets the airway-related adverse event was clinically similar, and in the intubation box the need for mask ventilation was maximum. The remaining airway-related adverse event was comparable across the aerosol protection equipment. Airway-related adverse event is airway-related adverse event, intubation box is intubation box, modified intubation box is modified intubation box, transparent sheets are transparent sheet and the airway-related adverse event is airway-related adverse events

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Intubation was considered to have failed completely if it took more than three attempts. Time to intubate (TTI) was defined as the time from removal of the facemark to achieving a capnography trace. After every use, the aerosol protection box was sanitised using medical-grade gadget sanitiser disinfectant. It was ensured that the anaesthesiologist would wear two gloves, one of which would be removed inside the aerosol box. The APE was again planned to be placed over the head end of the patient at the time of extubation.

The primary variable was taken as TTI and the secondary variables were desaturation, number of attempts and need to mask ventilate or use intubation aids or change the intubation device. The outcomes analysed were number of attempts, TTI, lowest SpO2, any adverse outcomes such as bucking, trauma and breaks in intubation with the need to ventilate in between attempts. These were considered airway-related adverse events (ARAE).

Statistical methods

With reference to the article by Begley et al.[5] which reports a median intubation time of 42.9 s with interquartile range (IQR) 32.9–46.9 for no aerosol box, and a median of 52.4 s with IQR 43.1 to for TTI. Standard deviation was estimated from the IQRs. These are 9.3 and 18.1, respectively. Fisher exact test was used for comparing numbers. Using these values and a power of 80% to detect a difference of at least 15 s in intubation time at a significance level of 5%, the sample size comes to a minimum of 14 in each group. The following formula has been used for this purpose of checking the statistical significance: Mann–Whitney test was used for two groups and Kruskal–Wallis test for three groups.

Study design

This was a retrospective observational study.

  Results Top

The airway management experience of 94 patients was analysed. The mean age of the patients was 47.6 years with 45 males and 49 females. Six anaesthesiologists participated in the study after familiarisation with the IB (first-generation) and with airway management protocol.

We found a statistically significant difference between TTI in median (IQR in minutes) between IB (4 [4–5]); TS (0.5 [0.3–0.5]) and MIB (0.3 [0.3–1.5]): P = 0.004). The participants themselves made the choice between CMac and McCoy laryngoscope; all intubations were carried out with stylet in situ. There was significant difference in TTI between devices; median (IQR in minutes) was McCoy (0.5 [0.3–2]), CMac (0.5 [0.3–1.5]): P = 0.004.

There was a significant difference in the number of attempts with the different methods used, that is, IB, TS and MIB. The number of attempts was also significantly different between the airway devices used [Table 1]. McCoy laryngoscope showed a significantly higher incidence of failed intubation (number of attempts >3): [Table 1], when compared to CMac D blade. Failed attempts increased the possibility of mask ventilation in between attempts, to maintain oxygenation. The ARAEs were more with the use of MacCoy laryngoscope [Figure 3]a. However, these events resolved spontaneously. [Figure 3]b shows that in MIB and TS the ARAE were clinically similar with respect to ARAE, in IB the need for mask ventilation was maximum. The remaining ARAE were comparable across the APEs; P > 0.05.
Table 1: Aerosol protection equipment

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No breach in PPE was experienced in any of the techniques. No patient had any recall of the placement of the aerosol box before induction of anaesthesia.

  Discussion Top

This study was undertaken to ascertain a secure airway management technique that will offer safety to the HCPs and the patient with minimal contamination of the OT environment.

Soon after securing the airway, the participating anaesthesiologists were questioned about their intubation experience. Three anaesthesiologists who used the IB had concerns about leak from the armholes and discomfort in performing airway management. Although the IB was intended to protect HCPs from viral exposure in the aerosols, the leak through the armholes and the open part of the box could potentially further increase the risk. No such concerns were raised in the MIB.

Several improvisations in the aerosol box have been pouring in from time to time.[5],[6],[7] The most recent adaptation at our centre and includes arm covers that we fixed to the armholes with specifications as per [Figure 1]. We used a suction catheter (200 mm Hg) through this for as much negative pressure as possible to suck out aerosols. The foot-end of the box has transparent plastic curtain to have an adjustable wall over patient's upper abdomen and to allow the assistant to pass his/her hand to assist the anaesthesiologist. A negative pressure of −1 to −3.5 was maintained in the operation theatre and a cooling time of 30 min was allowed between two surgeries.

It is imperative to carefully plan out the requirements and go through the steps and highlight any specific concerns before wheeling the patient into the OT. Each personnel must be clear about their duties at the time of anesthesia induction.

Although the patients that are for planned surgery come in with an RT-PCR negative report, there is a possibility of false-negative reporting. Hence, every step should be taken to prevent OT contamination and infection to the HCPs around in the OT.

The use of aerosol box increased the TTI and there were episodes of adverse events in the form of trauma and bucking, these were clinically insignificant.

It will be worthwhile to familiarise one's team with the use of the MIB, in view of the ongoing increase in the number of COVID cases. It certainly minimises the spillage of the aerosols. The heat and moisture exchanger with filter (HMEF) and the negative pressure attached to the ceiling of the box might add to the safety during airway management in the COVID times.

We did not examine the effect of the techniques used, on viral exposure to HCPs. However, out of 94 patients studied there were three patients who became symptomatic and tested positive on the third post-operative day. No HCP who was involved in the perioperative care of the patient developed symptoms or tested positive.

One limitation of this study we that we did not document how the TTI improved with the increasing number of intubation experiences with the MIB. All participants felt that there was the improvement in the ease of airway device placement with every usage.

The use of intubation/aerosol boxes certainly increase the TTI and expose patients to the risk of hypoxia and some adverse events; however, these adverse events were manageable and the minimum SpO2 that was encountered was 60% (in one patient), this was clinically insignificant and could be managed uneventfully. Even in the patients who required more attempts to device placement, there was no breach of PPE.

Video laryngoscope may be preferable to conventional laryngoscopes in view of higher incidence of failed attempts at intubation with the conventional laryngoscope. The bucking endangered the HCPs with possible exposure to the infected aerosols and was attributed to inadequate relaxation due to the use of precurarisation. Future research may focus on the benefits of complete relaxation using full dose of muscle relaxant.

  Conclusion Top

Video laryngoscope is favorable for managing airway in COVID-19 times. Suitable modifications in the first-generation IB, by including HMEF and a suction catheter in the design may offer good protection to the anesthesiologist and other care providers. In view of ongoing pandemic it might be worthwhile to include the MIB in the armamentarium and familiarize every anesthesiologist with its use.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.


We deeply acknowledge the support and guidance provided by Prof Abaya Indrayan, our biostatistician.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Tseng JY, Lai HY. Protecting against COVID-19 aerosol infection during intubation. J Chin Med Assoc 2020;83:582.  Back to cited text no. 1
Cook TM, El-Boghdadly K, McGuire B, McNarry AF, Patel A, Higgs A. Consensus guidelines for managing the airway in patients with COVID-19: Guidelines from the difficult airway society, the Association of Anaesthetists the Intensive Care Society, the Faculty of Intensive Care Medicine and the Royal College of Anaesthetists. ANAESTHESIA 2020;75:785-99.  Back to cited text no. 2
Malhotra N, Joshi M, Datta R, Bajwa SJ, Mehdiratta L. Indian Society of Anaesthesiologists (ISA National) advisory and position statement regarding COVID-19. Indian J Anaesth 2020;64:259-63.  Back to cited text no. 3
  [Full text]  
Patwa A, Shah A, Garg R, Divatia JV, Kundra P, Doctor JR, et al. All India Difficult Airway Association (AIDAA) consensus guidelines for airway management in the operating room during the COVID-19 pandemic. Indian J Anaesth 2020;64 Suppl S2:S107-15.  Back to cited text no. 4
Begley JL, Lavery KE, Nickson CP, Brewster DJ. The aerosol box for intubation in coronavirus disease 2019 patients: An in-situ simulation crossover study. Anaesthesia 2020;75:1014-21.  Back to cited text no. 5
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. 6
Leyva Moraga FA, Leyva Moraga E, Leyva Moraga F, Juanz Gonzále A, Ibarra Celaya JM, Ocejo Gallegos JA, et al. Aerosol box, an operating room security measure in COVID-19 pandemic. World J Surg 2020;44:2049-50.  Back to cited text no. 7


  [Figure 1], [Figure 2], [Figure 3]

  [Table 1]


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2004 Journal of Minimal Access Surgery
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