Aerosol and Droplet Dispersion During Gastrointestinal Motility Investigations

For droplet visualization, we will use fluorescein, which has been used for many years in medicine for diagnostic purposes and is safe upon topical administration, as a tracer. There are no local or systemic side effects of topical sodium fluorescein (5). Fluorescein is routinely used in the mouth to stain dental plaque (6). Through the lacrimal duct, the nasal cavity is exposed to fluorescein when it is used for ophthalmological purposes (7). Allergic reactions have been described to intravenous injection, which is not part of our trial. In the setting of head-and-neck and otolaryngological surgeries, coating the mouth with fluorescein has been used to quantify droplet spread, to assess for risk of transmission of COVID-19 (8). Hence, fluorescein can be safely applied to nasal and oropharyngeal cavities. We will use a similar approach, coating the nasal cavity, to study droplet spread from the nose during naso-gastric intubation for motility or reflux testing.

Quantification of aerosol will be done using a medical particle counter, as used for hospital safety measurements.