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

ObjectiveAerosol 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. DesignThis 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 0.3{micro}m-25{micro}m and 20{micro}m-3000{micro}m). Quantitative analysis was performed by recording specific events and subtracting the background particles. ResultsPOG 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. ConclusionsGastrointestinal 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. SIGNIFICANCE OF THIS STUDYO_ST_ABSWhat is already known on this subject?C_ST_ABSThe way we deliver healthcare has dramatically changed since the start of the COVID-19 pandemic. This includes gastrointestinal endoscopy, with precautions in place such as enhanced personal protective equipment, ventilation standards and prioritisation of procedures. Little research has been performed on establishing endoscopy as an aerosol generating procedure (AGP). Two recent studies indicate per-oral gastroscopy is an AGP. However, there is no data on the causative events within procedures, limited particle size analysis, and no data on trans-nasal endoscopy (TNE) or lower gastrointestinal (LGI) endoscopy. What are the new findings?This study greatly expands our knowledge of aerosol and droplet generation during gastrointestinal endoscopy. We show that per-oral gastroscopy (POG), TNE and LGI endoscopy all produce aerosols and droplets. We have quantified this to show that POG produces double the amount of background particles, whilst TNE produces half the particles and LGI a third lower particles than POG per unit time. We use a novel subtraction technique to analyse individual events within endoscopic procedures. This shows that anaesthetic spray is the major contributor for upper gastrointestinal (UGI) endoscopy, followed by coughing/gagging as well as extubation. For LGI endoscopy, the main contributors are rectal extubation, abdominal pressure application and rectal intubation, which produce more particles in the droplet range. All these events are at least comparable to volitional cough, whilst anaesthetic throat spray produces particle counts ten times higher. Furthermore, the presence of a hiatus hernia appears to increase particle generation for UGI endoscopy, whilst high patient discomfort does this for LGI endoscopy. Lastly, we show that particles sizes of some events, such as oral and rectal extubation, are significantly greater than the average particle size of a volitional cough. We also use a spray characteriser to show that particles of up to 300{micro}m are produced in UGI extubation and fundal retroflexion. How might it impact on clinical practice in the foreseeable future?The results in this study give important information for how we deliver endoscopy when there is a threat to the safety of healthcare workers and patients from transmissible infections. It is therefore relevant not only for the current COVID-19 pandemic, but also for other potential respiratory and gastrointestinal pathogens. 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. We show that for UGI endoscopy, alternatives to local anaesthesia spray would significantly reduce aerosol and droplet generation. The use of TNE would be desirable as it produces less aerosols than POG, but still additional mitigating strategies would be required. For LGI endoscopy, good technique that limits patient discomfort may mitigate aerosol and droplet generation. Further research needs to be done on infectivity of endoscopic procedures and barrier mitigating devices.