Patent ID: 7141037

Claim:
Apparatus for use in conjunction with a medical fluid infusion system for assessing the hazard to a patient connected to such infusion system of air in infusion fluid delivered along a fluid conduit of such system, the apparatus comprising: a sensor associated with the fluid conduit to detect air in the fluid passing along the fluid conduit of such infusion system and provide at time intervals output signals, each output signal corresponding to the amount of air in a predetermined section of said conduit at a sampling time within the respective interval; a memory adapted to store an air concentration value; a processor that receives the sensor output signal and each time the output signal is produced by the sensor, calculates a new air concentration value as the sum of (i) a raw value corresponding to the magnitude of the output signal and (ii) the product of an air concentration value previously stored in said memory and a weighting factor less than one, stores said new air concentration value in said memory in place of the previously stored air concentration value, compares said new air concentration value with a predetermined value, and provides an alarm signal if the new air concentration value calculated exceeds said predetermined value; a display connected with the processor for displaying said new air concentration value; and an alarm adapted to receive said alarm signal and operate when said new air concentration value has exceeded said predetermined value.