Identification of the source events for aerosol generation during oesophago-gastro-duodenoscopy

Abstract

ObjectiveTo determine if oesophago-gastro-duodenoscopy (OGD) generates increased levels of aerosol in conscious patients and identify the source events.DesignA prospective, environmental aerosol monitoring study, undertaken in an ultraclean environment, on patients undergoing OGD. Sampling was performed 20 cm away from the patient’s mouth using an optical particle sizer. Aerosol levels during OGD were compared with tidal breathing and voluntary coughs within subject.ResultsPatients undergoing bariatric surgical assessment were recruited (mean body mass index 44 and mean age 40 years, n=15). A low background particle concentration in theatres (3 L−1) enabled detection of aerosol generation by tidal breathing (mean particle concentration 118 L−1). Aerosol recording during OGD showed an average particle number concentration of 595 L−1 with a wide range (3–4320 L−1). Bioaerosol-generating events, namely, coughing or burping, were common. Coughing was evoked in 60% of the endoscopies, with a greater peak concentration and a greater total number of sampled particles than the patient’s reference voluntary coughs (11 710 vs 2320 L−1 and 780 vs 191 particles, n=9 and p=0.008). Endoscopies with coughs generated a higher level of aerosol than tidal breathing, whereas those without coughs were not different to the background. Burps also generated increased aerosol concentration, similar to those recorded during voluntary coughs. The insertion and removal of the endoscope were not aerosol generating unless a cough was triggered.ConclusionCoughing evoked during OGD is the main source of the increased aerosol levels, and therefore, OGD should be regarded as a procedure with high risk of producing respiratory aerosols. OGD should be conducted with airborne personal protective equipment and appropriate precautions in those patients who are at risk of having COVID-19 or other respiratory pathogens.

Quantitative evaluation of aerosol generation during manual facemask ventilation

“…Inter‐patient variation was considerable and ranged up to 50‐fold for tidal breathing and 36‐fold during coughing. This is in keeping with previous studies performed by the AERATOR group and others [ 6 , 8 , 11 , 12 , 16 ]. Therefore, using each participant as their own reference increases the power to generate meaningful comparisons from a relatively small sample.…”

“…Accumulating evidence demonstrates many procedures currently defined as aerosol generating are not intrinsically high risk for generating aerosol, and that natural patient respiratory events often generate far higher levels [ 6 , 7 ]. Furthermore, some of those procedures that generate aerosol, such as gastroesophageal endoscopy, only do so when the patient coughs [ 11 ]. The emerging evidence from quantitative clinical aerosol studies is yet to be incorporated into clinical guidance for aerosol generating procedures and we believe this needs urgent re‐assessment.…”

“…Based on previous work [ 6 ], the starting hypothesis was that facemask ventilation would produce no increase in aerosol above background. The sampling methodology was similar to previous work investigating aerosol production during gastro‐oesophageal endoscopy [ 11 ], where breathing was clearly distinguishable above background. Sample size calculations predicted 10 participants would ensure the study would be adequately powered to detect a difference of clinically important magnitude [ 13 ].…”

“…In brief, a prospective environmental monitoring study was conducted in operating theatres in a UK hospital (Southmead Hospital, North Bristol NHS Trust). All recordings were made within operating theatres with an ultraclean ventilation system (EXFLOW 32, Howorth Air Technology, Farnworth, UK) placed in standby mode [ 11 , 12 ]. This provides an environment with: very low background aerosol concentrations; an air change rate of 25 changes.h ‐1 (in line with most other operating theatres in the UK); an air velocity of 0.25 m.s ‐1 at 1 m above the ground; an air temperature of 20˚C; and relative humidity of 40–60%.…”

A quantitative evaluation of aerosol generation from upper airway suctioning during tracheal intubation and extubation sequences

“…All recordings were undertaken in operating theatres with ultraclean ventilation systems (EXFLOW 32, Howorth Air Technology, Farnworth, UK) placed in standby mode. We have previously described in detail the effect of placing this ventilation system in standby mode [8,9]. This results in an ultraclean environment with an air exchange rate equivalent to standard UK operating theatres.…”