Evaluation of a foldable barrier enclosure for intubation and extubation procedures adaptable for patients with COVID-19: A mannequin study

Dear Editor,

Aerosol contaminated with SARS-CoV-2 can spread out, even when wearing full personal protective equipment (PPE). Therefore, protective box covering patient's head during airway management should be useful. One such simple protective box with two circular openings was recently presented by a Taiwan anaesthesiologist [1]. At first, it got a lot of attention, but a number of limitations were soon pointed out: size constraints, problem with storage, limited dexterity in manipulating the tracheal tube, lack of access for a nurse anaesthetist etc. [2]. Furthermore, the feasibility of airway management associated with the use of such protective box has not yet been evaluated [2].

Considering these limitations, we designed a modified version of the box (Fig. 1B,C). It is made of acrylic glass and aluminium, and can easily be disinfected. Additional openings were added for the nurse anaesthetist's hands. The position of the box can be adjusted in cranio-caudal direction. The access holes for the hands are closed with overlapping neoprene that closes the access hole even when the hands are inside (Fig. 1D). The side toward the patient's legs is closed with polypropylene fabric. The air is constantly removed from the box through filters with one or two standard aspirators, ensuring box air volume exchange every 3 min [3]. Additional ports for an aspirator, a ventilation hoses and monitoring cables were added. The box is foldable, which facilitates storage, permits modification and replacement of only individual parts, and can be installed around already intubated patients in different settings. To test feasibility of airway management with such protective box, we assessed the time to tracheal intubation, first-pass success rate, and the possibility of maintaining patent airway using simple manoeuvres with and without it. We additionally evaluated the contamination of neoprene closure when hand is pulled out of the box (Fig. 1D,E,F).

Fig. 1.

Time to airway device placement (A) using direct laryngoscopy (DL), Airtraq, C-MAC and I-Gel with () and without (■) protective box (n = 36). Values are median, inter-quartile-range and range. *p < 0.05 vs. airway device placement time without the protective box (Wilcoxon signed-rank test). Inside view (B) of the protective box. Lateral view (C) of the protective box. Simulation of droplet contamination of the gloves (D) with red colour. Access hole closure was contaminated (painted) only on the inner side (E), while it stayed uncontaminated (F) on the outer side when the contaminated hand was pulled out of the box. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

The study was approved by the Institutional Review Board of University Medical Center Ljubljana. Thirty-six experienced board-certified protective box-naïve anaesthetists participated in the study. After giving the written informed consent, each anaesthetist was asked to perform tracheal intubation on an airway training manikin (Airway Management Trainer, Ambu, St Ives, UK) by direct laryngoscopy (DL) and videolaryngoscopy (VL) using Airtraq® (Prodol Meditec, Vizcaya, Spain) and C-MAC® (Karl Storz, Tuttlingen, Germany), and to insert I-Gel® supraglotic device (Intersur-gical Ltd.; Workingham, UK), with and without the protective box. They were randomised into two groups, one started with the protective box, and the other without it. The following parameters were measured: time to airway device placement (defined as the interval between grasping the laryngoscope/I-Gel and first successful breath indicated by the manikin), rate of first-pass success and visual analogue scale (VAS) for airway device placement and patent airway maintenance difficulty with and without protective box (subjectively assessed by the anaesthetist on a 100 mm scale ranging from 0 = extremely easy to 100 = extremely difficult). Anaesthetists were instructed to intubate with a 7.0 mm I.D. cuffed tracheal tube with guide wire (Portex SoftSeal, Portex, Hythe, Kent, UK) as they would routinely do in a patient without difficult airway starting from face mask ventilation, with the help of nurse anaesthetist (Fig. 1C). Values are median [IQR].

The use of protective box prolonged the time to intubation (Fig. 1A), with no significant difference in first pass success rate (94.4% with vs. 95.4% without the protective box, p = 0.99, Chi-square test). Anaesthetists assessed that airway device placement was more difficult with than without the use of the protective box in all simulated approaches: DL (VAS 28 [15–59] with vs. 11.5 [4–24] without protective box, p = 0.0001), VL (VAS 14 [7–20] with vs. 7 [1–14] without protective box, p = 0.0009) and I-Gel® (VAS 16 [4–25] with vs. 9 [1–24] without protective box, p = 0.0258, Wilcoxon signed-rank test). All anaesthetists performed face mask ventilation and extubation procedure successfully with and without protective box, assessing that they would be able to maintain patent airway using jaw thrust (VAS 8 [2–21]) and face mask (VAS 9 [3–18]) inside protective box.

The protective box prolonged the time to tracheal intubation and may represented a limitation for anaesthetists. However, our results suggest that on average the prolongation time (of 9 s with DL and 4 s with VL) is probably not clinically relevant. Since extubation procedures bear significantly higher risk (0.2–6%) [4] of contact between patient sputum and the eye-, nose- or mouth-region of the healthcare worker than intubation procedures, we believe that such protective box would be especially useful for extubation procedures, to minimize the risk of contamination of the procedure room. We must nevertheless emphasize that the guidelines for PPE should be strictly maintained, and new protective devices developed during the current healthcare crisis should be applied cautiously, only as an additional protection and not as replacement for standard PPE [5].

Declaration of competing interest

We declare that the contents have not been published and are not being submitted elsewhere. The manuscript has been read and approved by all co-authors. The authors declared no conflict of interest. This work was supported by the Slovenian Research Agency (grant P3-0043).