Method for discriminating between operating conditions in medical pump

Abstract

A method is disclosed for determining the operating condition of a medical pump based on data derived from a pressure sensor and a position sensor. The pressure sensor generates pressure data by sensing the force on the pumping element. The position sensor generates position data by tracking the pumping cycle and determining the position of the pumping element. The pump pressure data and pump position data are processed and the calculated results compared with a pre-determined threshold value to determine the operating condition of the pump. The three main types of operating conditions of concern are the following: normal condition, where liquid is present and no leaks exist in pumping chamber; leak condition, where liquid is present but a leak exists in the pumping chamber; and air stroke condition, where the chamber contains some air.

1 . A method for determining operating conditions in a medical pump having a cassette with a pumping chamber, comprising:
 monitoring the pump cycle with a position sensor;   starting a testing timer for a pre-determined test time at a specified portion of the pump cycle;   closing the pumping chamber to flow during at least a portion of the specified portion of the pump cycle;   acquiring a plurality of pressure reference values during a first portion of test time from a single pressure sensor;   calculating and storing a pressure anchor value by averaging the reference values;   setting a first prior integration term of zero;   acquiring a pressure data value from the pressure sensor;   calculating and storing a new integration term by subtracting the anchor value from the data value to obtain a resultant, multiplying the resultant by a weighting value to obtain a product, and adding the product to the prior integration term;   repeating the steps of acquiring the pressure data value and calculating and storing the new integration term until the pre-determined test time has expired; and   comparing the new integration term with a pre-determined threshold value to determine the operating condition of the pump.