Image analysis
shadows
After scanning, data were input into the picture archiving and communication system of Hunan Provincial People’s Hospital (The First Affiliated Hospital of Hunan Normal University) for image evaluation. The main observations were as follows: the presence of any clear gas shadows along the direction of venous inflow (superior vena cava, right atrium, right ventricle, and main pulmonary artery) within the examination area and the location, number, and diameter of the shadows. The air emboli were graded, and their diameter was measured according to the methods of Groell et al. [