Quantifying aerosol and droplet generation during upper and lower gastrointestinal endoscopy: whole procedure and event-based analysis

Phillips, F. M.; Crowley, J.; Warburton, S.; Gordon, G. S. D.; Parra-Blanco, A.

Objective Aerosol generating procedures have become an important healthcare issue due to the COVID-19 pandemic, as the SARS-CoV-2 virus can be transmitted via aerosols. We aimed to characterise aerosol and droplet generation in gastrointestinal endoscopy, where there is little evidence. Design This prospective observational study included patients undergoing routine per-oral gastroscopy (POG, n=36), trans-nasal endoscopy (TNE, n=11) and lower gastrointestinal (LGI) endoscopy (n=48). Particle counters took measurements near the appropriate orifice (two models used, diameter ranges 0.3um-25um and 20um-3000um). Quantitative analysis was performed by recording specific events and subtracting the background particles. Results POG produced 2.06x the level of background particles (p<0.001), and 2.13x the number of particles compared to TNE. LGI procedures produce significant particle counts (p<0.001), with a rate of 8.8x106/min/m3 compared to 13.0x106/min/m3 for POG. Events significant relative to the noise floor of background particles were: POG- throat spray (112.3x, p<0.01), oesophageal extubation (36.7x, p<0.001), coughing/gagging (30.7x, p<0.01); TNE- nasal spray (32.8x, p<0.01), nasal extubation (25.6x, p<0.01), coughing/gagging (23.3x, p<0.01); LGI- rectal intubation (3.5x, p<0.05), rectal extubation (11.8x, p<0.01), application of abdominal pressure (4.9x, p<0.05). These all produced particle counts larger than or comparable to volitional cough. Conclusions Gastrointestinal endoscopy performed via the mouth, nose or rectum all generates significant quantities of aerosols and droplets. As the infectivity of procedures is not established, we therefore suggest adequate PPE is used for all GI endoscopy where there is a high population prevalence of COVID-19. Avoiding throat and nasal spray would significantly reduce particles generated from UGI procedures.