Change of Gastric Fluid Volume After Oral Hydration in Fasted Objects

Observations of two kinds of liquids (water, carbohydrate drink) in five different volumes (10ml, 50ml, 100ml, 200ml, 400ml) will be performed on different days. Subjects prepare for investigation, a 4-hour fast excluding water, followed by 1 hour of fasting including water, and then 10 ml or 50 ml or 100 ml or 200 ml or 400 ml of clear water in a pre-randomized order and then the cross-sectional area of the stomach antrum will be measured via ultrasound every 10-minute until the contents are no longer visible. The same observation will be performed with a noNPO drink beverage containing 50 g of carbohydrate, again in a randomized order, and then 10 ml, 50 ml, 100 ml, 200 ml or 400 ml, and then every 10 minutes until the contents are no longer visible. One dose of one type of fluid will be ingested and observed at each visit, and repeated visits will be made until observations for all doses have been completed (10 visits in total, with 5 doses of water and carbohydrate drinks). During measurement, the stomach will be checked for contents supine position and then turned to the right decubitus.