Fig. 1

Ultrasonic examination of the gastric antrum. A:The Sonosite M-Tube to was used for monitoring, with the 2–5 MHz convex array probe. The patient lies on the right side (supine position for patients who cannot lie on the right side due to critical condition). The head of the bed is raised 30–45 degrees, and the direction of the probe is parallel to the longitudinal axis of the body, under the xiphoid process. Clear gastric antrum ultrasound was obtained at the right side of the median sagittal line [5]. B: Schematic diagram of standard section:L: liver. A: antrum of stomach. P: pancreas. SMA:superior mesenteric artery. Ao: aortaventralis