Introduction

Covid-19 pandemic has affected healthcare workers (HCW) worldwide. Anaesthesiologists, being at the frontline, are at increased risk of exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) while performing aerosol-generating procedures like intubation and extubation in the operating rooms (ORs) and intensive care units (ICUs). Limited availability of personal protective equipment (PPE) and the need to safeguard HCW from aerosol exposure, has led to the development of various protective measures, one of them being the intubation box. An intubation box is a transparent box, that may be used for intubation and/or extubation. The first intubation box was designed by Dr Lai Hsien Yung [1]. Since then, intubation boxes of various designs and dimensions have been devised during these pandemic times to reduce the exposure risk [2,3,4,5,6,7]. Few simulation studies are being done to access the efficacy and safety and to evaluate the pragmatic use of these boxes [2,3,4]. However, the utility of these boxes, the ease of performing intubation and/or extubation, and difficulties faced in a real-time scenario needs further evaluation. This study was aimed to address this very issue and an observational questionnaire-based study was formulated to evaluate the experience of anaesthesiologists while performing intubation and extubation with the intubation box.

Materials and Methods

After approval from the Institutional Ethical Committee and CTRI registration no. REF/2021/04/043083, this cross-sectional questionnaire-based observational study was conducted at a tertiary care centre between August to October 2021. Patients were briefed about the procedure involved and prior written informed consent was obtained. For this study, a transparent intubation box made of acrylic was innovated named as “Abhedya” [Fig. 1]. It has walls on three sides and the box was open on the foot end. The left-sided wall had two circular self-sealing ports each to admit both the hands of an assisting anaesthesiologist and another one for the introduction of suction catheter. Whereas the right-sided wall had two self-sealing ports for the insertion of inspiratory and expiratory limbs of the breathing circuit and another one as suction port. The wall at the head end had two similar ports, for admitting the hands of the anaesthesiologist performing the intubation. After putting the box over the patient’s head, it was sealed from the foot end with a transparent plastic curtain and an additional Velcro sheet was used to seal it from all the sides. This box was used for all abdominal and lower limb surgeries needing endotracheal intubation where it can be kept in place throughout the procedure till extubation. After shifting the patient to OR, the protective box was placed over the patient’s head and all the equipments required for intubation were placed inside it including direct laryngoscope, face mask attached to breathing circuit, endotracheal tube (ETT) of appropriate sizes, 10 ml syringe for inflation of ETT cuff, tapes for securing of ETT, intubation aids like stylet and bougie, and two suctions, one to create negative pressure and the other for oral and endotracheal suction. Intubation was performed and assisted by two different anaesthesiologists and the intubation box was kept in place throughout the procedure till extubation. After that, the intubation box was removed and cleaned for reuse using 1% sodium hypochlorite solution. A total of 21 intubations were done using this box. The experience of participants was recorded via a Google Form and one response per participant was restricted. A valid response, within the stipulated time, was received from 25 anaesthesiologists who were either performing or assisting the intubation. The Google form consisted of 24 questions regarding the time taken to intubate, number of attempts, Cormack-Lehane grading, ease of performing intubation and using intubation aids, the manoeuvrability of hands while handling instruments, visibility through the box, stability of the box, ease of removal of the box, cognitive comfort and suggestions for improvement.

Fig. 1
figure 1

The Protective Box “Abhedya”

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Statistical Analysis

Data from the questionnaire was compiled and analysed using descriptive statistics. SPSS (Statistical Package for Social Sciences) software version 23. Categorical and nominal variables were expressed as numbers and percentages and were analysed using the Chi-square or Fischer’s exact test. A p-value less than or equal to 0.05 was taken as statistically significant.

Results

The intubation box was used by anaesthesiologists with varying levels of experiences and included resident doctors in training and those doing senior residency [Table 1]. Of the total, 40% (n = 10) were senior resident while those in first, second and third year of residency constituted 12% (n = 3), 24% (n = 6) and 24% (n = 6) respectively.

Table 1 Questionnaire
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Of the total respondents, majority (n = 17, 68%) performed the intubation themselves while the remaining assisted (n = 8, 32%). Most (n = 20, 80%) were either sensitized or given demonstration earlier for proper use of intubation box. Most (84%) reported prior use of the intubation box on an earlier occasion. Majority (n = 24, 96%) used the intubation box where difficult airway was not anticipated, except for only one case.

More than half (52%) of the respondents took approximately 1–3 min to intubate, while 40% could do in less than 1 min. Whereas, only in 8% of cases time taken to intubate was longer than 3 min. Almost 84% of the anaesthesiologists were able to intubate in the first attempt while 2 or 3 attempts were required by only 4% and 8% respectively. Most (n = 14, 56%) reported Cormack- Lehane grade 1 of laryngoscopy. While 24%, 16% and 4% of respondents found Cormack-Lehane grade of 2a, 2b and 3b respectively.

Majority reported (n = 23, 92%) clear visibility through the box while only 8% (n = 2) reported poor visibility. Very poor visibility was reported by none of the participants. While 88% found it easy or manageable to perform procedures like oropharyngeal suctioning, video laryngoscopy or supra-glottic airway insertion with the intubation box, and only 12% found it difficult. Most (n = 21, 84%) didn’t need intubation aids and the majority (72%) found it either easy or manageable to manoeuvre hands while inserting and handling instruments with the intubation box. 21 out of the 25 respondents (84%) found it either easy or manageable to communicate with the patients while using the intubation box and only 16% found it difficult.

Most (76%) found the cognitive comfort to be comfortable or equivocal as compared to 40% finding it uncomfortable. The use of intubation box was ergonomic comfortable with 80% of them. In none of the cases, a breach in PPE was reported.

The entire procedure was completed with the intubation box in place most of the times (n = 19, 76%). The intubation box had to be removed during intubation in only 1 case and during extubation in 4 cases due to difficulty in handling the airway. None reported any difficulty in removal of the box with most (n = 24, 96%) feeling that it was either manageable or easy. The box was found to be stable by 16 participants (64%) while 8 (32%) reported the need for assistance to hold the box and only 1 (4%) found it very unstable. No injury to the patient or health care worker was reported with the use of the intubation box.

Most (n = 18, 72%) opined that more practice before using the box would have improved their overall experience and all except one, recommended the usage of intubation box in terms of efficiency and safety. None of the participants suggested any further improvement for the existing Intubation Box.

To evaluate the effect of the experience of respondents, responses of junior resident doctors in the first and second year of training (Group 1) were compared with third-year residents and senior residents (Group 2) [Table 2]. There was a significant difference in the time taken to intubate between the two groups (p = 0.048) and it was found that Group 2 with more experience took less time to intubate (only 6.25% required > 3 min to intubate versus 11.1% in Group 1). Also, significantly more respondents in Group 2 found it easier to manoeuvre the hands to handle instruments than Group 1(p = 0.024). Whereas no significant difference was found in terms of the number of attempts of intubation, visibility through the box, communication with the patient, performing suctioning and other procedures, cognitive comfort and ergonomic aspect in the two groups.

Table 2 Comparison of use and safety between Group 1 and 2
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Discussion

The current Covid-19 pandemic has flooded the healthcare facilities with an unusually large number of patients who require oxygen support due to respiratory failure and require mechanical ventilation (3–15%) [8, 9]. The risks to HCW are compounded by a large number of intubations which is a highly aerosol-generating procedure.

The efficacy of protective box to reduce aerosol exposure has been a topic of debate with studies supporting its use as an adjunct to PPE and others suggesting otherwise. Based on such studies, FDA has recently revoked the use of passive intubation box citing that such boxes “may not be effective in decreasing HCW exposure to airborne particles and may instead contribute to an increase in HCW exposure to airborne particles” [7, 10].

Since the first design of aerosol box [1], many innovations have been incorporated in their design to improve their functioning and safety [2,3,4,5,6,7]. Our main design modifications were done to minimise exposure of aerosols to HCW, includes self-sealing ports for the clinician performing and assisting the intubation and two separate self-sealing ports for suction channels. Also is the transparent sheet with Velcro sealing the foot end of the box.

Also, continuous negative pressure was maintained within this box by catheter with the running suction machine to prevent the expulsion of aerosols from these boxes, thus providing additional protection to HCW’s from the heavy viral load [11]. The application of negative pressure in isolation room is already in use in many centres and has been recommended to prevent the spread of any airborne infection especially COVID-19 [12,13,14,15]. In our study, as high as 92% of participants were able to intubate in less than 3 min with 84% being able to intubate in the first attempt which corroborated with study of Wakabayashi et al. who concluded that the increase in intubation time was not clinically relevant [16]. Our observations also revealed that the clinicians with more experience [Group 2] took significantly less time to intubate [Table 2]. Thereby, suggesting that the use of intubation box by experienced doctors would alleviate the concern of increased procedural times.

The use of intubation box has been described to cause reduced dexterity and manoeuvrability of hands by few authors in the past [3]. But, in our study, almost 72% of the respondents found it easy or at least manageable to manoeuvre the hands while intubating with the box. In addition, sub-group analysis also revealed that more respondents in the experienced group [Group 2] found it easier to manoeuvre the hands.

Almost all the respondents (96%) have recommended the use of intubation box based on their experience in terms of efficiency and safety.

One of the limitations of our study was that we were able to collect few responses due to the box being recently innovated. Another limitation was that the efficacy of box in reducing aerosol exposure was not measured. Also, the utility and comfort of using intubation box in patients with difficult airway cannot be evaluated by our study. The use of this intubation box with video-laryngoscope and for fiberoptic intubation needs to be evaluated further.

Conclusion

We recommend that usage of intubation box during intubation or extubation is a non-harmful and necessary compromise that we must make to protect the/ safeguard the well-being of HCW without affecting patient care in our fight with COVID-19. We conclude that the minor limitations of visibility, manoeuvrability, performance, ergonomic and cognitive comfort while using them, can easily be overcome by design modifications and with experience and practice.