2.3. Study design
TB, ’ bowel preparation
ADVERSE EFFECTS
After the patients were hospitalized, they underwent bowel cleansing by drinking 2 L of PEG plus ascorbic acid solution using the split-dose method. Briefly, 1 L of PEG plus ascorbic acid solution was administered in 2 doses, that is, once the night before the test and on the morning of the day of the test. Patients were divided into 5 groups according to the simethicone administration time: 4 experimental groups and 1 control group. Patients were randomized to each of the experimental group. The control group did not receive simethicone treatment. The experimental groups were divided into the following subgroups according to the timing of simethicone administration: the day before the examination and before bowel cleansing (BB); the day before the examination and after bowel cleansing (BA); the day of the examination and before bowel cleansing (TB); and the day of the examination and after bowel cleansing (TA). Simethicone was administered orally at a dose of 200 mg (10 mL). For bowel cleansing, patients drank 1 L of solution for 2 hours from 8 PM to 10 PM the day before the test and drank the remaining 1 L for 2 hours from 6 AM to 8 AM on the day of the test. Because the patients only needed to drink the solution in a set amount of time, the start and end times could not be controlled equally for everyone (see Fig., Colonoscopy was performed between 11 AM and 4 PM. Before the test, the patients completed a questionnaire about the time to take simethicone, the time to finish taking a bowel cleansing agent, and adverse effects after taking simethicone. The endoscopist who performed the colonoscopy was blinded to the time of simethicone administration of the patient. Five experts who performed more than 2000 cases in total and more than 300 cases per year performed colonoscopy examinations. The bubble score (BS) scale was used to evaluate the number of bubbles, which is as follows: 3 (<5% of bubbles covering mucosa, no obscuration), 2 (5%–25% of bubbles covering the mucosa, mild obscuration), 1 (25%–50% of bubbles covering the mucosa, moderate obscuration), 0 (>50% of bubbles covering the mucosa, severe obscuration).After the colonoscopy examination, the endoscopists recorded BS, ABPS, and the number of irrigations of the simethicone-mixed solution for the right colon, transverse colon, and left colon. They also recorded the satisfaction score of patients’ bowel preparation with a numeric rating (0–10, 0: very bad, 10: excellent). To reduce variation and equalize the evaluation criteria among endoscopists, a guideline paper was attached to every endoscopy room, and the endoscopist performed calibration exercises on scoring systems before and after the examination (see Fig., 