Air filtration mitigates aerosol levels both during and after OGD procedures

ObjectivesUpper GI endoscopies are aerosol generating procedures (AGPs), increasing risk of spreading airborne pathogens. We aim to quantify mitigation of airborne particles via improved ventilation, specifically laminar flow theatres and portable HEPA filters, during and after upper GI endoscopies. MethodsThis observational study included patients undergoing routine oral gastroscopy in a standard endoscopy room with 15-17 air changes per hour, a standard endoscopy room with portable HEPA filtration unit, and a laminar flow theatre with 300 air changes per hour. A particle counter (diameter range 0.3{micro}m-25{micro}m) took measurements 10cm from the mouth. Three analyses were performed: whole procedure particle counts, event-based counts and air clearance estimation using post-procedure counts. ResultsCompared to a standard endoscopy room, for whole procedures we observe a 28.5x reduction in particle counts in laminar flow (p<0.001) but no significant effect of HEPA filtration (p=0.50). For event analysis we observe for lateral flow theatres reduction in particles >5{micro}m for oral extubation (12.2x, p<0.01), reduction in particles <5{micro}m for coughing/gagging (6.9x, p<0.05) and reduction for all sizes in anaesthetic throat spray (8.4x, p<0.01) but no significant effect of HEPA filtration. However, we find that in the fallow period between procedures HEPA filtration reduces particle clearance times by 40%. ConclusionsLaminar flow theatres are highly effective at dispersing aerosols immediately after production and should be considered for high-risk cases where patients are actively infectious or supply of PPE is limited. Portable HEPA filers can safely reduce fallow time between procedures by 40%.