RESUMO
Aerosol generating procedures (AGPs) are defined as any procedure releasing airborne particles <5 m in size from the respiratory tract. There remains uncertainty about which dental procedures constitute AGPs. We quantified the aerosol number concentration generated during a range of periodontal, oral surgery and orthodontic procedures using an aerodynamic particle sizer, which measures aerosol number concentrations and size distribution across the 0.5-20 m diameter size range. Measurements were conducted in an environment with a sufficiently low background to detect a patients cough, enabling confident identification of aerosol. Phantom head control experiments for each procedure were performed under the same conditions as a comparison. Where aerosol was detected during a patient procedure, we assessed whether the size distribution could be explained by the non-salivary contaminated instrument source in the respective phantom head control procedure using a two-sided unpaired t-test (comparing the mode widths (log({sigma})) and peak positions (DP,C)). The aerosol size distribution provided a robust fingerprint of aerosol emission from a source. 41 patients underwent fifteen different dental procedures. For nine procedures, no aerosol was detected above background. Where aerosol was detected, the percentage of procedure time that aerosol was observed above background ranged from 12.7% for ultrasonic scaling, to 42.9% for 3-in-1 air + water syringe. For ultrasonic scaling, 3-in-1 syringe use and surgical drilling, the aerosol size distribution matched the non-salivary contaminated instrument source, with no unexplained aerosol. High and slow speed drilling produced aerosol from patient procedures with different size distributions to those measured from the phantom head controls (mode widths log({sigma})) and peaks (DP,C), p< 0.002) and, therefore, may pose a greater risk of salivary contamination. This study provides evidence for sources of aerosol generation during common dental procedures, enabling more informed evaluation of risk and appropriate mitigation strategies.
RESUMO
BackgroundTransmission 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. MethodsReal-time, high-resolution environmental monitoring was conducted in ultraclean ventilation operating theatres. Continuous sampling with an optical particle sizer allowed characterization of aerosol generation within the airway management zone during endotracheal intubation and extubation for urgent orthopaedic trauma or neuro-surgery. ResultsAerosol 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 aerosolized particles (maximum concentration, 80{+/-}10 L-1,n=14, P<0{middle dot}001 vs cough). Extubation, particularly when the patient coughed, produced a detectable aerosol plume but with a smaller number of particles (<25%) than a volitional cough. ConclusionsUsing 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 an AGP. Extubation does generate aerosols, particularly if the patient coughs, but these are weaker than a standard reference. These findings indicate the need for a reappraisal of guidance on PPE for AGPs.
