Reducing droplet spread during airway manipulation: lessons from the COVID-19 pandemic in Singapore

Editor—Coronavirus disease 2019 (COVID-19) was declared a pandemic by the World Health Organization¹ on March 11, 2020 because of its rapid worldwide spread. In the operating theatre (OT), anaesthetists are taking precautions for every patient to minimise perioperative viral transmission as infected patients can be asymptomatic.² Airway manipulation poses a high risk of viral transmission to humans within close contact because of the proximity of the respiratory secretions that can aerosolise from coughing and gagging.³ Supplementary Fig 1 from Chan and colleagues⁴ shows the dispersion of respiratory particles: the dispersion distance of exhaled air can range from 42 to 99 mm, and from coughing bouts after intubation up to 460 mm.

The Singapore General Hospital instituted guidelines for airborne and contact precautions, including (i) environmental, reducing staff during airway manipulation, regular disinfection and sterilisation, sufficient air exchange time; and (ii) personal protective equipment (PPE). We identified a potential shortcoming in that none of these measures reduced the production and spread of respiratory secretions, which contain the bulk of the viral burden. Decontamination of the OT depends on adequate cleaning of OT equipment and reduction of viral load by high-frequency air changes. There is a long period between intubation and extubation, in which respiratory droplets remain on surfaces before cleaning. We describe some practical innovations that anaesthetists can consider integrating into their workflow. These innovations are not meant to replace PPE, but aim to reduce the cumulative risk of perioperative viral transmission to all the personnel in the OT. In countries where doctors are advised to reuse PPE because of shortages, these may afford an extra degree of protection.

Plastic tent or screen for intubation

Supplementary Figs 2 and 3 were taken from a simulation run for proof of concept. All volunteers gave their consent. The appropriate PPE for intubation was not worn in this simulation to conserve supplies.

The main aim of constructing a tent or screen is that, if the patient coughs/gags during intubation, secretions will land under the sheet. Making the tent involves combining two transparent plastic bags into a single bag large enough to be draped over the patient's head to chest. Two drip stands are used to hold the tent up. A videolaryngoscope and tracheal tube can be passed under the plastic tent for intubation. The C-MAC® (KARL STORZ Endoscopy (UK) Ltd) videolaryngoscope is shown because it has an external screen outside the tent that would provide a clear laryngoscopy view. The tent is disposed and the drip stands wiped down.

Alternatively, Supplementary Fig 4 shows the use of a large plastic screen for intubation. The same plastic sheet is draped over the patient's head and chest after inducing unconsciousness, and taped down at the sides to minimise leak. Intubation is performed with the aid of the McGRATH™ (Medtronic, USA) videolaryngoscope because of ease of cleaning compared with the C-MAC®. The plastic sheet can be left in the same position for the duration of the operation. If the patient needs to be in a lateral or beach chair position, the sheet is shifted correspondingly over the face.

The advantage of the tent is its low cost, easy availability, and disposability. It allows room for manoeuvring the tube and is tall enough to allow a bougie in. The length of the tent is sufficient to fall past the patient's pillow so that there is no contact between the intubating personnel and the patient. This protective tent can be modified for use in ICUs during suctioning, bronchoscopy, and other aerosol-generating procedures. The screen is similar to the tent and provides a tighter seal. We suggest leaving adequate holes at the sides and the head end for the airway team to access the patient.

There are reports of using acrylic boxes with preformed armholes for intubation.^{5 , 6} However, that requires time and cost for manufacturing and delivery before it is available. The armholes, being of fixed shape and size, limit dexterity in manipulating the tracheal tube, especially in difficult airways. The bottom panel of the box is left open, which runs the risk of the assistant standing there being exposed to aerosolised respiratory secretions.

Plastic screen for extubation

Supplementary Fig 5 shows use of a plastic screen for extubation. A small hole is cut distally to allow the ventilator tubing to pass through. If the patient coughs, secretions will land on the plastic sheet. A potential window of infection exists when the tracheal tube is removed with secretions at the cuff before it is thrown into the bin. We suggest for the tracheal tube to be wrapped with a plastic bag and immediately disposed.

Hudson mask for extubation

Supplementary Fig 6 shows the two holes at the sides of a Hudson mask (Teleflex, USA) being taped up using a transparent dressing. The Hudson mask is placed over the patient's face following intubation, and the tracheal tube passes under the Hudson mask. At extubation, the Hudson mask is connected to oxygen, and a suction catheter is passed under the Hudson mask into the patient's mouth. Once the patient is ready for extubation, the tracheal tube and the suction catheter are removed from under the mask and discarded immediately. Should the patient cough post-extubation, secretions are contained within the mask. The patient can then be transferred out of the OT with the Hudson mask for oxygen supplementation.

In summary, these low-cost, accessible, and disposable methods can reduce contamination by respiratory secretions at the source. They may add another layer of protection from perioperative viral transmission during outbreaks of highly infectious diseases, such as COVID-19, especially in the context of acute shortages of PPE.

Authors' contributions

Study design: both authors

Drafting of article: PSAY

Reviewing of article: both authors

Declarations of interest

The authors declare that they have no conflicts of interest.

Handling editor: Hugh C Hemmings Jr

Appendix A. Supplementary data

The following is the Supplementary data to this article: