Study objective: To clarify the risk of exposure to the exhaled aerosol droplets from patients for medical staffs during digestive endoscopy via labelling the oral mucosa with vitamin B2 solution, and evaluate the protective efficacy of personal protective equipment.

Study design: This is a prospective randomized controlled study.

This is a prospective randomized controlled study. Patients who meet the inclusion criteria and do not meet the exclusion criteria are recruited for this trial. They will be randomly divided into the control group and the intervention group (A total of 70 subjects, and 35 per group based on calculation of sample size). The in vitro bionic model next to the doctor simulated a medical staff, which is printed via the stereolithographic appearance 3D printing technique following the morphological structure data of human face and airway obtained by processing CT images, will either wear a mask or not, depending on the intervention group (in the intervention group, in vitro model wears personal protective equipment). Before starting the esophagogastroduodenoscopy (EGD) under anesthesia, vitamin B2 saline solution (vitamin B2 dosage determined by the suggested daily nutrient uptake in China) is dripped in their mouths. When the examination is finished, the dosage of facial mucosa deposition and airway inhalation of the in vitro model is quantified as a cumulative droplet mass (μg) over all the exposure time. The deposited droplets are collected by wiping method, and the inhaled droplets are sampled by a solution-based sampler (SKC, U.S.A.). The dosage is detected by the Fluoro Max-4® fluorophotometer (HORIBA, Japan). By comparing and analyzing the results of the two intervention groups, the researchers try to evaluate the risk of exposure under the personal protective equipment and assess the effectiveness of it.

Inclusion Criteria:

• During the study period, patients who were treated in the digestive endoscopy center of Peking Union Medical College Hospital and planned to undergo digestive endoscopy. Age and gender are not limited temporarily.

Exclusion Criteria:

• Patients who have ever been allergic to the medical non-toxic fluorescent agent ( vitamin B2 saline solution).
• Patients who received anti-tumor therapy during the period of digestive endoscopy.
• Patients with poor general conditions, including severe cardiopulmonary diseases, coagulation disorders, or a total of platelet less than 50*10^9/L.
• Patients with structural pulmonary disease (chronic obstructive pulmonary disease, asthma, etc.) or airway/pulmonary surgery history
• Patients with intolerance or contraindications to digestive endoscopy.