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%.

Bronchoscopy masks mitigate aerosols during upper gastrointestinal endoscopies

“…A number of protective barriers have been proposed to minimise that risk. Continuous suction of the oral cavity [1], shielding barriers [6,7], masks [8,9], and increasing the distance between patient and endoscopist [10] and improved ventilation such as laminar flow theatres [11] have been proposed as methods to reduce the exposure of endoscopists and endoscopy staff to aerosols. Here, we present a study that uses masks that are clinically approved for bronchoscopy (Explorer endoscopy facemask, Intersurgical Ltd., United Kingdom) to attenuate aerosol production at the patient's mouth (bare mask shown in Fig.…”

Cytosponge procedures produce fewer respiratory aerosols and droplets than oesophagogastro-duodenoscopies

“…Aerosols can remain airborne for many hours before depositing in the lower airways, whereas droplets land quickly and can contaminate surfaces: these two size ranges therefore represent two key routes of transmission for respiratory viruses such as a SARS-CoV-2. OGD procedures therefore present significant occupational risk to healthcare workers, necessitating the use of mitigation strategies including use of high-grade personal protective equipment 4 , improved ventilation 5,6 , increased fallow periods 7 and alternative procedures (e.g. transnasal endoscopy) 1 .…”