The disease COVID-19 has been classified as pandemic by World Health Organisation (WHO) in March 2020. This poses a risk to healthcare workers. Whether esophagogastroduodenoscopy (EGD) is a aerosol-generating procedure (AGP) has brought controversy. Multiple international guidelines consider EGD as AGP based on expert consensus. No scientific data has been published regarding this. With a commercially available particle counter, we can differentiate the particle counts of different sizes in different areas of the endoscopy room. An increase from baseline particles of < 5um during or after the procedure would suggest that the procedure is an AGP. The baseline particle counts before and during the procedure are also recorded. The details of the procedure including procedure time and the use of sedation are also documented.

The disease COVID-19 has been classified as pandemic by World Health Organisation (WHO) in March 2020. This poses a risk to healthcare workers. Whether esophagogastroduodenoscopy (EGD) is a aerosol-generating procedure (AGP) has brought controversy. Multiple international guidelines consider EGD as AGP based on expert consensus. No scientific data has been published regarding this. Currently, the term droplet is often taken to refer to droplets >5 microns (μm) in diameter that fall rapidly to the ground under gravity, and therefore are transmitted only over a limited distance (e.g. ≤1 m). In contrast, the term droplet nuclei refers to droplets ≤5 μm in diameter that can remain suspended in air for significant periods of time, allowing them to be transmitted over distances >1 metre. With a commercially available particle counter, we can differentiate the particle counts of different sizes in different areas of the endoscopy room. An increase from baseline particles of < 5um during or after the procedure would suggest that the procedure is an AGP. With the use of a commercial available particle counter, the number of particles of size (0.3um, 0.5um, 0.7um, 1um, 5um and 1um) are recorded. The baseline particle counts before and during the procedure are also recorded. The details of the procedure including procedure time and the use of sedation are also documented.

Inclusion Criteria:

• All patients undergoing EGD in the endoscopy unit of Prince of wales Hospital, Shatin, Hong Kong

Exclusion Criteria:

• EGD cannot be completed due to patient's condition
• Patients who are unstable and require extra medical attention
• Patients who refuse
• Patients who are not fit for consent

All patients undergoing EGD in the endoscopy unit of Prince of wales Hospital, Shatin, Hong Kong will be included