Air filtration mitigates aerosol levels both during and after endoscopy procedures

Abstract

Objectives: Upper gastrointestinal endoscopies are aerosol-generating procedures, increasing the risk of spreading airborne pathogens. We aim to quantify the mitigation of airborne particles via improved ventilation, specifically laminar flow theatres and portable high-efficiency particulate air (HEPA) filters, during and after upper gastrointestinal endoscopies.

Methods: This observational study included patients undergoing routine upper gastrointestinal endoscopy in a standard endoscopy room with 15-17 air changes per hour, a standard endoscopy room with a portable HEPA filtration unit, and a laminar flow theatre with 300 air changes per hour. A particle counter (diameter range 0.3 μm-25 μm) took measurements 10 cm from the mouth. Three analyses were performed: whole procedure particle counts, event-based counts, and air clearance estimation using post-procedure counts.

Results: Compared 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 μm for oral extubation (12.2x, p < 0.01), reduction in particles <5 μm for coughing/gagging (6.9x, p < 0.05), and reduction for all sizes in anesthetic 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%.

Conclusions: Laminar 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 the supply of personal protective equipment is limited. Portable HEPA filers can safely reduce the fallow time between procedures by 40%.

Keywords: COVID‐19; aerosols; air conditioning; endoscopy; infection control.