Why the interest?

The combination of a deadly contagion (COVID-19) and recognition that endotracheal intubation is a high risk procedure for the airway technician has lead to the development of novel medical equipment. One such innovation is the clear-perspex 'intubating box' designed to contain viral-aerosols released during intubation. There has been limited prior evaluation of the safety or efficacy of such devices, despite their promotion.

What did they do?

Begley et al. conducted 36 simulated intubations with twelve PPE-adorned¹ anaesthetists, with and without intubating boxes. They primarily aimed to quantify the effect on time to intubation.

Investigators tested both a first-generation and newer generation device. Each of twelve senior anaesthesiologists performed three block-randomised intubations: no box, original, and latest-design box. The airway manikin tongue was inflated to simulate a grade 2A airway.

And they found...

Intubation time was significantly increased by both the older and newer box designs (x̄=48s and x̄=28s longer respectively, though with wide confidence intervals). More relevantly there were frequent prolonged-duration intubations with the box (58% >1 minute, 17% >2 min), but none without the box.

Most worrying, there were eight breaches of PPE caused by box use, seven occurring with the newer, more advanced design.

"PPE breaches often seemed to go unrecognised by participants, potentially increasing their risk further."

Reality check

Despite the superficial appeal of an intubation box, this simulation study warns that such devices fail both to support safe and timely intubation and to protect the clinician – the very arguments used to advocate for its use.

These failings occur before even considering the actual effectiveness in reducing viral exposure, the box's impact on emergent airway rescue, or the practicality of cleaning a reusable device now coated with viral particles.

The intubating aerosol box appears dead on arrival.

Bonus biases

Begley notes the appeal of such novel devices may be partly driven by 'gizmo idolatry' (Leff 2008) and 'MacGyver bias' (Duggan 2019), blinding clinicians to consider unknown consequences of box use and discounting resultant hazards.

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1. Local COVID PPE guidelines were used: face-shield, goggles/glasses, mask, gown & gloves. ↩

summary

• J L Begley, K E Lavery, C P Nickson, and D J Brewster.
• Intensive Care Unit, Cabrini Hospital, Malvern, Vic, Australia.
• Anaesthesia. 2020 Aug 1; 75 (8): 1014-1021.

AbstractThe coronavirus disease 2019 pandemic has led to the manufacturing of novel devices to protect clinicians from the risk of transmission, including the aerosol box for use during tracheal intubation. We evaluated the impact of two aerosol boxes (an early-generation box and a latest-generation box) on intubations in patients with severe coronavirus disease 2019 with an in-situ simulation crossover study. The simulated process complied with the Safe Airway Society coronavirus disease 2019 airway management guidelines. The primary outcome was intubation time; secondary outcomes included first-pass success and breaches to personal protective equipment. All intubations were performed by specialist (consultant) anaesthetists and video recorded. Twelve anaesthetists performed 36 intubations. Intubation time with no aerosol box was significantly shorter than with the early-generation box (median (IQR [range]) 42.9 (32.9-46.9 [30.9-57.6])s vs. 82.1 (45.1-98.3 [30.8-180.0])s p = 0.002) and the latest-generation box (52.4 (43.1-70.3 [35.7-169.2])s, p = 0.008). No intubations without a box took more than 1 min, whereas 14 (58%) intubations with a box took over 1 min and 4 (17%) took over 2 min (including one failure). Without an aerosol box, all anaesthetists obtained first-pass success. With the early-generation and latest-generation boxes, 9 (75%) and 10 (83%) participants obtained first-pass success, respectively. One breach of personal protective equipment occurred using the early-generation box and seven breaches occurred using the latest-generation box. Aerosol boxes may increase intubation times and therefore expose patients to the risk of hypoxia. They may cause damage to conventional personal protective equipment and therefore place clinicians at risk of infection. Further research is required before these devices can be considered safe for clinical use.© 2020 Association of Anaesthetists.

This article appears in the collection: Anaesthesiology, Personal Protective Equipment (PPE) and COVID.

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