Flow Sensor Calibrated by Volume Changes

Abstract

An infusion pump and method are provided which combine flow rate measurements calibrated by accurate volume measurements over time.

Description

BACKGROUND[0001]The present disclosure relates to fluid flow control systems, such as intravenous infusion pumps, and more particularly to feedback control infusion pumps with flow and volume sensing.[0002]In some situations, such as with intravenous infusions, the flow rate range requirement is very broad, covering more than four orders of magnitude of rate, e.g., from about 0.1 ml per hour to about 6,000 ml per hour. If any sort of low flow rate sensitivity is to be expected, then the response of a flow sensor should be logarithmic or at least non-linear. The absolute calibration of such a flow sensor would be very challenging, especially at low flow rates. Even without the requirement for calibration, it is difficult to find a commercially available flow sensor that services this flow rate range.[0003]Certain infusions have historically been managed by air pressure delivery systems, most commonly found in the operating room and in emergency situations. Prior art attempts have bee...

AI Technical Summary

Benefits of technology

[0007]An advantage of the present disclosure resides in its accuracy. The present disclosure offers two novel views of flow control, one operating over many minutes, and the other operating many times per second, which is analogous to having both a speedometer and an odometer, so that a steady speed may be maintained, while still making adjustments to arrive at one's destination on time. The high degree of accuracy is advantageous for infusion of vasoactive drugs, since the flow should be as continuous as possible and the flow rate resolution should be high enough to resolve a 1% change in requested flow rate. Likewise, for long term doses (e.g., 12-72 hours), it is important to complete the dose on time. Also, for longer-term infusions, the accuracy of the system should not degrade over time. There are clinical and operational problems with infusions that are completed too soon (e.g., increased chance of clotting off the IV line) or too late (e.g., unused medication, biohazard, etc.). For intermittent infusions, the time the dose starts is important, so that the peak serum levels of the intermittent medication occur as ordered. For market acceptance, the device should perform well according to worldwide testing standards, including the integrated flow volume “trumpet curve.”

[0008]An additional advantage of the present disclosure resides in its simplicity. Instead of a complex electromechanical assembly of gears, levers, motors, and switches, a sensor-based flow regulation system can be relatively simple and low cost in its construction.

[0010]In certain embodiments, the present disclosure is capable of operating over an extended range of flow rates, e.g., from below 1 milliliter per hour to 6,000 milliliters per hour. At all flow rates, the fluid flows continuously without the characteristic flow disruptions of a typical motor driven large-volume pump.

Problems solved by technology

There are clinical and operational problems with infusions that are completed too soon (e.g., increased chance of clotting off the IV line) or too late (e.g., unused medication, biohazard, etc.).

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