2. Principle of pressure difference: Some advanced infusion devices, such as electronic infusion pumps, use atmospheric pressure difference to drive liquid flow. In this device, the infusion bag is usually located at a lower position, and the infusion tube is connected to a syringe or a pump. When the required flow rate and pressure are set, the pump will generate a negative pressure area, so that the liquid can be pumped in and sent to the patient through the pipeline. Atmospheric pressure here plays a key role in promoting liquid flow.