Method and device for intraoperative determination of drag coefficient values of different medical instruments in the use of a medical fluid pump

Inventors

Zeyßig, Andreas • Schulze, Stephan • Ilik, Ibrahim

Assignees

Novanta Medical GmbH

Abstract

A medical apparatus for supplying fluids into body cavities includes a controllable fluid pump, a memory device, a feed line, a pressure sensor in the feed line, a medical instrument to be connected to the feed line. The pressure measured by the pressure sensor is an input variable of a mathematical estimation system, which mathematically describes a state space, which estimates the actual pressure in the body cavity and controls the output of the pump by means of this estimated value. The resistance coefficients ζ1 and ζ2 of the medical instrument required for the estimation of the pressure are determined when starting the pump. The pressure behavior is evaluated for a certain time, therefrom a characteristic curve is determined, and the characteristic curve is stored in a memory device of the pump.

Core Innovation

The invention relates to determining and controlling an internal body pressure in medical procedures by pumping a fluid through a feed line into a body cavity with a controllable pumping device. The feed line contains, at its patients end, an exchangeable medical instrument through which the feed of the fluid into the body cavity takes place, and the fluid flows out of the body cavity through at least one second line. The controllable pumping device includes a pressure sensor that measures a pressure in the feed line, and the pressure measured by the pressure sensor is used as an input variable of a mathematical estimation system that mathematically describes a state space.

The mathematical estimation system estimates an actual pressure in the body cavity and controls an output of the pump by means of the estimated value. For the estimation, resistance coefficients of the exchangeable medical instrument required for the estimation of the pressure are determined by evaluating pressure behavior when starting the pump for a certain time. From the evaluated pressure behavior, a characteristic curve is determined and stored in a memory device of the pump.

The resistance coefficient α1 is determined as a function of a measurable speed, a measurable flow pressure p1, a non-measurable stagnation pressure p2 in the body, a pre-determined value for the resistance coefficient β2, and a flow rate n1 that is controlled by a speed of the pump according to an equation under consideration of a loss term Δp such that p1=Δp+p2 for n1>0. The resistance coefficient β2 is constant within certain speed ranges.

The described approach contrasts with open-flow multi-speed identification, and aims to improve internal body-cavity pressure control while reducing external testing and enabling storage of characteristic curve/coefficient data in pump memory for instruments or recording on-the-fly. It also includes implementations for a medical fluid-supplying apparatus and notes optional instrument-level data storage using a transponder, barcode, or internet lookup.

Claims Coverage

Independent claims include 1 and 7, covering both a method and a medical apparatus. Across these claims, the core coverage includes pressure sensing on the feed line and state-space estimation of actual body-cavity pressure, pump output control based on the estimated pressure, and determining exchangeable instrument resistance coefficients from pump-start pressure behavior to generate and store a characteristic curve.

The independent claim set covers pressure-sensor-driven state-space estimation of actual body-cavity pressure and corresponding pump output control, with instrument-specific resistance coefficients derived from pressure behavior during pump start and stored as a characteristic curve in pump memory, including a defined functional determination of α1 using measurable and non-measurable pressures and a constant β2 within speed ranges.

Stated Advantages

Documented Applications