Air filtration mitigates aerosol levels both during and after OGD procedures

Abstract

Objectives: Upper 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. Methods: This 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 0.3um-25um) 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. 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 >5um for oral extubation (12.2x,p<0.01), reduction in particles <5um 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%. 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 supply of PPE is limited. Portable HEPA filers can safely reduce fallow time between procedures by 40%.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

The authors also thank Nottingham University Hospitals NHS Trust for funding the rental of the N60 spray characteriser and rental of a particle counter, Norgine Pharmaceuticals for sponsoring the purchase of a particle counter, and Olympus Medical UK for providing the endoscopes for transnasal endoscopy. GSDG would like to acknowledge a UKRI Future Leaders Fellowship (MR/T041951/1).

Author Declarations

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Wales Research Ethics Committee gave ethical approval for this work (IRAS 285595)

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Data Availability

Data associated with this publication is available at http://dx.doi.org/10.17639/nott.7112 Code used for data analysis in this publication can be found at https://github.com/gsdgordon/aerosols

http://dx.doi.org/10.17639/nott.7112

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