Gastric fluid analysis
BANG
To rule out the risk of pulmonary aspiration due to chewing gum intervention, the estimated volume and acidity of gastric fluid were compared between the two groups. Before induction of anesthesia, a gastric ultrasound scan was performed on the operating table by a single experienced investigator (YJ Bang) to estimate gastric fluid volume. We measured gastric antrum cross-sectional area (CSA) using the free tracing method on the portable ultrasound unit. Gastric fluid volume was estimated by the following formula: Gastric fluid volume (mL) = 27.0 + 14.6 x Right–Lateral CSA (cm