Evaluation of the Comparative Risk of Aerosol Generation by Tracheal Intubation and Extubation in the Operating Theatre

Abstract

Background: Transmission of SARS-CoV-2 by bioaerosols is of increasing concern. The enhanced levels of personal protective equipment (PPE) and preventative measures to attenuate viral transmission during aerosol generating procedures (AGPs) are having a huge impact on healthcare provision. There is no quantitative evidence on the number and size of airborne particles produced during AGPs to inform risk assessments. Methods: Real-time, high-resolution environmental monitoring was conducted in ultraclean ventilation operating theatres. Continuous sampling with an optical particle sizer allowed characterisation of aerosol generation within the airway management zone during endotracheal intubation and extubation for urgent orthopaedic trauma or neuro-surgery. Findings: Aerosol monitoring showed a very low background particle count allowing resolution of the transient airborne particle plume produced by reference volitional coughs (maximum concentration, 1,690±140 particles.L‑1,n=38). By comparison, endotracheal intubation including mask ventilation produced negligible quantities of aerosolised particles (maximum concentration, 80±10 L‑1,n=14, P<0·001 vs cough). Extubation, particularly when the patient coughed (~50% of extubations), produced a similar size distribution of aerosolised particles to the reference cough but contained a smaller number of particles (<25%). Interpretation: Using a volitional cough as a reference we have been able to produce a relative risk ranking for endotracheal intubation and extubation as potential AGPs. The study does not support the assignation of endotracheal intubation by direct laryngoscopy with manual ventilation as AGPs in routine anaesthetic practice. Extubation does generate aerosols, particularly if the patient coughs, but these are weaker than a standard reference cough and this challenges the designation of extubation as being a higher risk event for airborne vector transmission. These findings indicate the need for urgent reappraisal of guidance on PPE and patient management for AGPs. Funding: Supported by Elizabeth Blackwell Institute with funding from the University of Bristol’s alumni and friends. BRB is supported by the Natural Environment Research Council (NE/P018459/1). Declaration of Interest: None to declare Ethical Approval Statement: Not needed