A system for detecting and removing a gas bubble from a vascular infusion line, the system comprising: a disposable cassette adapted for disposition intermediate the fluid line, the disposable cassette comprising: a body; and a flexible hollow tube having an inlet port being configured for connection to the supply side of the fluid line, an outlet port being configured for connection to the patient side of the fluid line and a purge port located intermediate the inlet port and the outlet port; a base unit adapted to receive the disposable cassette and monitor fluid flow through the flexible hollow tube, wherein the base unit comprises: a sensor adapted to detect the presence of a gas bubble in the fluid flowing through the flexible hollow tube; and a pinch valve adapted to stop the flow of fluid through the flexible hollow tube; and an electronic control unit adapted to operate the base unit so that (i) fluid is permitted to flow past the pinch valve when no gas bubble is detected by the sensor; and (ii) fluid flow is arrested when a gas bubble is detected by the sensor, characterized in that a) the flexible hollow tubing is arranged in a switchback configuration so as to create a sensor loop, so that two portions (L1,L2) are adjacent to one another, and b) the sensor is adapted to simultaneously detect the presence of a gas bubble in the fluid flowing through at least two portions (L1,L2) of the flexible hollow tube. a disposable cassette adapted for disposition intermediate the fluid line, the disposable cassette comprising: a body; and a flexible hollow tube having an inlet port being configured for connection to the supply side of the fluid line, an outlet port being configured for connection to the patient side of the fluid line and a purge port located intermediate the inlet port and the outlet port; a body; and a flexible hollow tube having an inlet port being configured for connection to the supply side of the fluid line, an outlet port being configured for connection to the patient side of the fluid line and a purge port located intermediate the inlet port and the outlet port; a base unit adapted to receive the disposable cassette and monitor fluid flow through the flexible hollow tube, wherein the base unit comprises: a sensor adapted to detect the presence of a gas bubble in the fluid flowing through the flexible hollow tube; and a pinch valve adapted to stop the flow of fluid through the flexible hollow tube; and a sensor adapted to detect the presence of a gas bubble in the fluid flowing through the flexible hollow tube; and a pinch valve adapted to stop the flow of fluid through the flexible hollow tube; and an electronic control unit adapted to operate the base unit so that (i) fluid is permitted to flow past the pinch valve when no gas bubble is detected by the sensor; and (ii) fluid flow is arrested when a gas bubble is detected by the sensor, characterized in that a) the flexible hollow tubing is arranged in a switchback configuration so as to create a sensor loop, so that two portions (L1,L2) are adjacent to one another, and b) the sensor is adapted to simultaneously detect the presence of a gas bubble in the fluid flowing through at least two portions (L1,L2) of the flexible hollow tube. a) the flexible hollow tubing is arranged in a switchback configuration so as to create a sensor loop, so that two portions (L1,L2) are adjacent to one another, and b) the sensor is adapted to simultaneously detect the presence of a gas bubble in the fluid flowing through at least two portions (L1,L2) of the flexible hollow tube.