Medical Devices

Abstract

To determine the resistance coefficients in particular of different combinations of a shaft cylinder and an endoscope when using a medical fluid pump in the context of arthroscopy.SOLUTION: Provided is a method for determining and controlling the internal body pressure in medical methods, wherein a fluid is pumped by a controllable pumping device through a feed line into a body cavity, wherein the feed line contains, at its patient's end, a medical instrument, through which the feed of the fluid into the body cavity takes place, wherein the fluid can flow out of the body cavity through a second line, wherein the pump included in the pumping device is controlled, wherein the feed line contains a pressure sensor that measures the pressure in the line, wherein the pressure measured by the pressure sensor is an input variable of a mathematical estimation system, which mathematically describes a state space, and which estimates the actual pressure in the body cavity and controls the output of the pump by means of this estimated value, wherein the resistance coefficients ζ1 and ζ2 of the medical instrument required for the estimation of the pressure are determined by that 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.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The subject of the present invention is in particular a method for determining the resistance coefficients of various barrel and endoscope combinations when using a medical fluid pump, for example in connection with arthroscopy. [Background technology]

[0002] In various medical procedures inside the body, fluids, such as gases or liquids, are introduced into and removed from the body. One example of this is arthroscopy, where, for example, in connection with a knee joint examination or treatment procedure, the knee is irrigated with an irrigation fluid. Another exemplary procedure is laparoscopy, where a gas (e.g., CO2) is introduced into the body during the treatment procedure. 2 ) are introduced into the body. For these procedures, the measurement, control and mainly the limitation of the pressure in the body is of particular importance. For therapeutic procedures, it is particularly necessary to ensure a certain fluid flow rate, for example to flush smoke or blood from the body, while at the same time limiting the pressure in order not to damage the body tissue. For this purpose, various devices and methods are available.

[0003] In order to avoid the various drawbacks of the conventional methods, a method and an apparatus directed thereto are presented, which determine the internal pressure during pump operation very accurately without the need for pressure sensors in the body cavity (Patent Document 1). In this method, data from a pressure sensor external to the respective body cavity is used as the basis for estimating the internal pressure. For the internal pressure estimation, a mathematical model is used, which describes by a set of differential equations the entire medical system consisting of a pressure controller, a controllable pump motor, a supply channel, a pressure sensor, a medical supply device (e.g. a barrel with an endoscope), a body cavity and, possibly, a fluid outlet (e.g. an aspiration device) and combines them in a so-called state space model. Details are given in Patent Document 1.

[0004] As found during operation of such systems, many of the estimated critical parameters of the individual components described above remain substantially constant. However, it has also been found that various medical delivery devices (e.g., various applicable barrels) exhibit widely varying parameters, particularly flow parameters. Depending on the barrel and endoscope combination in use (hereafter also referred to as the instrument), widely varying pressure drops will occur.

[0005] Therefore, for the operation of a medical fluid pump, the respective resistance coefficient (see below) must be measured for each device before starting. This measurement can be carried out, for example, for an "open flow measurement", by generating a liquid flow and measuring the pressure drop relative to the ambient pressure. This measurement is of course carried out outside the joint. The resulting flow pressure corresponds to the device pressure, i.e. the resistance coefficient of the basic combination of barrel and endoscope. The disadvantages of this measurement method are obvious: the most important disadvantage of this measurement method is that such a measurement must be performed after every device change, i.e. when changing devices during surgery. The disadvantages here are in particular the time required, which is at least 15 to 30 seconds. Moreover, it is disadvantageous that a certain amount of fluid that cannot be further used must be used for the measurement. Such time and fluid requirements are simply unacceptable for practitioners who deal with such systems.

[0006] If we consider the pressure along the fluid flow between two particular system locations to be the same flow velocity and constant density at that point, the relationship shown in Equation 1 becomes:

[0007]

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[0008] For example, Δp represents the pressure drop across the barrel and endoscope use combination from the pressure difference between the flow pressure in the hose and the stagnation pressure in the joint (the so-called instrument pressure). The stagnation pressure in the joint is a controlled pump variable and is not measured for the reasons mentioned above. To determine the pressure in the joint, the instrument pressure must be measured in addition to the measurable flow pressure. For this, the characteristic curve is fitted with the dimensionless resistance coefficient ζ according to Equation 2: 1 and ζ 2 It can be found based on the following.

[0009]

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[0010] Using Equation 2 in Equation 1, P 2 By rearranging the equation for the statistical measurement, Equation 3 becomes:

[0011]

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[0012] Here, the left side of the equation (^P 2 ) represents an estimate of the joint pressure. To determine the resistance coefficient of equation 2, at least three pairs of values ​​(Δp) must be recorded for three different flows (n1). Such measurements are shown in Figure 1. Now, three different flows are adjusted and the respective pressure differentials are measured. After a certain time, a final value without fluctuations is obtained, as shown in Figure 1 (top). The flow adjustments are performed by controlling the motor speed of the pump. The pressure determination is performed in open flow mode, i.e. with respect to ambient pressure. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] International Publication No. 2015 / 144120 Summary of the Invention [Problem to be solved by the invention]

[0014] The above method has several disadvantages: 1) To get the most accurate drag coefficient possible, you must wait until each signal reaches its final value without any fluctuations. 2) At least three speed ranges must be run to determine the drag coefficient, otherwise there will be no solution for the basic equation system. 3) The time required for adjustment of the stable final value in combination with the required speed range makes it possible to improve the time period for the application of device recognition outside the joint. 4) The procedure is not suitable for performing instrument identification (i.e., determining instrument pressure) at the joint, which may lead to excessive overpressure at the joint. 5) The fluids required for the measurements are not used in surgical procedures.

[0015] It is therefore an object of the present invention to simplify the measurement of the resistance coefficient for various devices, which measurement is carried out more quickly and mainly in the body (e.g. in the joints) and consumes as little fluid or gas as possible. [Means for solving the problem]

[0016] A solution to this object is provided by the method according to claim 1, namely pumping the fluid through the supply passageway and into the body cavity with a controllable pumping device; the delivery channel includes a replaceable medical device at a patient end thereof through which fluid delivery into the body cavity is effected; a second passageway through which fluid can flow from the body cavity; Controlling a pump included in the pumping device; At least the supply flow path includes a pressure sensor for measuring a pressure in the flow path; The pressure measured by the pressure sensor is an input variable of a mathematical estimation system that mathematically represents a state space, and the input variable is used to estimate the actual pressure in the body cavity and to control the output of the pump based on this estimate. 1. A method for determining and controlling intracorporeal pressure in a medical procedure, comprising: Resistance coefficient ζ of medical equipment required for pressure estimation 1 and ζ 2 is determined by determining a characteristic curve from evaluating the pressure behavior over a certain period of time when the pump is started and storing the characteristic curve in a memory device of the pump. It is characterized by method This is achieved by:

[0017] In the method according to the invention, the resistance coefficient ζ can be calculated already during one start of a pump with acceptable accuracy. 1 and ζ 2 is determined. Higher accuracy is achieved when several starts are performed. Two starts of the pump were found to be the optimum.

[0018] The term "starting the pump" particularly includes the change of the pump output from 0 ml / min to a pump output adapted to the desired equipment and intended use (e.g. 25 l / min for suction or 500 ml / min for arthroscopy), for example by integrating a peristaltic roller pump under adjustment of the target speed. In special cases, measurements can also be carried out to change the pump from a low output to a significantly higher output (e.g. from 2.5 l / min to 25 l / min for suction or from 50 ml / min to 500 ml / min for arthroscopy). This is also included in the term "starting the pump". Such an embodiment is less preferred and requires an adaptation of the calculations presented below, in particular the calculation of the pressure loss term Δp.

[0019] A solution to the above object further comprises a device according to claim 6, namely a medical device for supplying a fluid into a body cavity, comprising a controllable fluid pump, a memory device, a supply channel, a pressure sensor in the supply channel and a medical instrument connected to the supply channel, the pressure measured by the pressure sensor is an input variable of a mathematical estimation system that mathematically represents a state space, the input variable being used to estimate the actual pressure in the body cavity and the output of the pump being controlled by this estimate; Resistance coefficient ζ of medical equipment required for pressure estimation 1 and ζ 2 is determined by determining a characteristic curve from evaluating the pressure behavior over a certain period of time when the pump is started and storing the characteristic curve in a memory device of the pump. It is characterized by Medical devices, This is achieved by: [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 represents measurements recorded for at least three pairs of values ​​(Δp) for three different flows (n1) to determine the resistance coefficient of Eq. 2. [Diagram 2] FIG. 2 illustrates, in simplified form, a number of characteristic curves showing the characteristic curves of various devices. [Diagram 3] FIG. 3 shows how to determine the loss term Δp for calculating ζ1 according to Equation 4. [Figure 4] FIG. 4 shows a possible program sequence. [Diagram 5] FIG. 5 shows data from actual pressure measurements in an articulation dummy (shown in black) compared with estimated data from a system according to US Pat. No. 5,999,333 (shown in grey). [Figure 6] FIG. 6 shows data from actual pressure measurements in an articulation dummy (shown in black) compared with estimated data from a system according to the invention (shown in grey). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Therefore, to compensate for the disadvantages of the open circulation method described above, the following measurement method is proposed:

[0022] For a given medical liquid pump, in a first test series several characteristic curves are recorded. For this purpose, the equipment provided for the liquid pump operation (i.e. the barrel and endoscope combination) is connected to the pump and the respective flow-dependent equipment pressures are measured and evaluated. The measured values ​​for a specific equipment can be expressed as a characteristic curve. A number of characteristic curves showing such characteristic curves for different equipment are illustrated in simplified form in FIG. 2. It can be seen that the different resistance characteristics of the equipment depend mainly on the effective flow cross-section. It can also be assumed that other physical dependencies will behave in a time-invariant manner. As a result, different resistance coefficients (ζ) depending on the flow cross-section are obtained. 1 , z and ζ 2 , z) are obtained, where "z" is the number of recorded characteristic curves. From these characteristic curves, ζ 2 The values ​​are stored as a priori knowledge in a memory device of the pump.

[0023] Other methods are conceivable for measuring and storing the characteristic curves. It is also possible to measure all approved devices and store the resistance coefficients or characteristic curves when the pump is manufactured. - In another embodiment, the procedure of measuring and storing the resistance coefficients or characteristic curves is carried out prior to each application, i.e. after the respective device is connected to the pump. Although pumps with certain stored characteristic curves are available on the market, it is of course also possible for the user to carry out additional measurements of resistance coefficients or characteristic curves individually for his preferred devices and store them in addition to the already stored data.

[0024] In both cases, the measurement procedure can be started anew before or during the operation, so that intraoperative adaptation is possible.

[0025] To derive an algorithm for device recognition in the body (e.g., at a joint), the polynomial described in Equation 2 is rewritten as follows:

[0026]

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[0027] Equation 4 expresses the flow resistance ζ1 The measurable velocity, measurable flow pressure p1, and immeasurable stagnation pressure P in the body 2 , and flow resistance ζ 2 The flow resistance ζ is expressed as a function of a given value for 2 is assumed to be constant within a certain speed range. ζ is more suitable for short-term constant speed supply. 2 The value of ζ is obtained by increasing the pressure. 2 The value of is selected from memory.

[0028] According to Eq. 4, ζ 1 To calculate this, the loss term Δp must be determined. This is shown in Figure 3:

[0029] For the calculation of the pressure loss term Δp, the following conditions: (t 1 -t 0 ) and t 3 > n for a period of 0 1 =0 for p 1 =p 2 n 1 >0 for p 1 =Δp+P 2 applies.

[0030] Considering the above conditions, time t 2 The stagnation pressure p 2 The determination is made after the dynamics of the measurement signal drops at time t ≥ t 3 The loss term is the difference (p 1 -p 2 ) due to

[0031] It must be taken into account that the calculation accuracy of Δp depends on the amount of possible leakage. If the determined instrument parameters are outside the valid range, a characteristic curve stored in memory is selected.

[0032] Comparing the method according to the present invention to the prior art methods described above shows the unexpected advantages of the present invention: The conventional method (open flow method) uses the resistance coefficients ζ1 and ζ 2 Determining the flow rate requires three different flow adjustments to the pump. In comparison, the method according to the present invention requires only one or two activations of the pump. The method according to the invention takes only about 7 seconds (with two starts of the pump) compared to 15-30 seconds for certain prior art methods. Prior art identification methods must be performed outside the body. The identification method according to the present invention is in principle performed inside the body, but can also be performed outside the body. Prior art identification methods are time consuming. The user must wait during the procedure until he can initiate his own intervention. The method according to the invention works during application in the background and the user is not affected by it. After the identification methods of the prior art, the surgeon cannot immediately start with the intervention. For this reason, he must first generate a specific fluid flow in the body (before inflation). With the method according to the invention, in principle, the fluid flow generated for the identification is already used for the pre-dilatation of the body cavity. The amount of unused fluid is thus minimized.

[0033] Overall, there are therefore substantial advantages in terms of speed and ease of use. It is particularly important that the accuracy of the method according to the invention corresponds approximately to that of the known prior art methods. Figure 5 shows data of actual pressure measurements in a joint dummy (shown in black) compared to estimated data of a system according to US 2007 / 0139997 (shown in grey). The actual values ​​are never greater than the estimated values, and usually these values ​​are also slightly smaller than the estimated data, which is preferred for safety reasons. Figure 6 shows data of actual pressure measurements in a joint dummy (shown in black) compared to estimated data of a system according to the invention (shown in grey). Again, the actual values ​​are never greater than the estimated values, and usually these values ​​are also slightly smaller than the estimated data, which is preferred for safety reasons. As a result, approximately equal pressure estimation accuracy is observed at the joints.

[0034] The invention also relates to a device for carrying out the method according to the invention, namely a medical fluid pump for irrigating a body cavity, for example a joint cavity. The device can be a liquid pump, as well as an aspirator. A liquid pump operating in the peristaltic roller pump mode is preferred according to the invention. The controlled pump supplies fluid to a body cavity, for example a knee joint, through a hose and a medical device, for example a barrel with an optical system. The body cavity may also include a device for draining the liquid. The pump is operated in accordance with the intention to generate an overpressure in the body cavity, which opens (distends) the cavity. In the device according to the invention, the above-mentioned internal pressure is determined by estimation. A pressure sensor located in the hose or outside the body cavity at the hose determines pressure data which represent input parameters for the estimation. This mathematical estimation system describes a state space, whereby the actual pressure in the body cavity is estimated and the pump output is controlled by this estimate. Such a device is described in the patent application WO 2005 / 023363. In addition to the pump, the device according to the invention comprises an additional memory for storing the results of the a priori knowledge.

[0035] The memory device can be implemented on a non-replaceable chip (e.g. EPROM). Alternatively, other, in particular replaceable or modifiable, memory media are of course conceivable. It may also be provided to update, e.g. modify the memory device or the stored data, by replacing the memory device or importing new data via a corresponding interface. Importing new data may also optionally be performed via the Internet, and of course the security of the import operation must be ensured, in particular with regard to the authenticity of the data source.

[0036] To determine a priori knowledge of the characteristic curve, a pump manufacturer can, for example, measure all equipment provided for the pump (i.e., all combinations of barrels and endoscopes) and store the measurement data in a memory device of each pump prior to shipment.

[0037] Alternatively and / or additionally, measurement data can be provided in which different equipment is simulated by the proportional valve, since as mentioned above different resistance characteristics of the equipment depend primarily on the effective flow cross section which can be simulated by different settings of the proportional valve.

[0038] Alternatively and / or additionally, a drag coefficient ζ provided by instrumental measurements 1 and ζ 2 can be stored in the memory device of any pump. As soon as the pump is put into operation, the data of the pressure sensor, i.e. the pressure obtained in the hose, is compared with the stored characteristic values. The resistance coefficient that is most likely to match the measured data is selected, and the resistance coefficient ζ 1 and ζ 2 is used in conjunction with an estimation system for estimating intracorporeal pressure.

[0039] A possible program sequence is shown in Figure 4.

[0040] The method according to the invention and the device according to the invention can work with various fluid drainage devices. Drainage can be passively ensured from the body cavity through an opening (e.g. an incision) or a hose. A pump can also be provided to pump the fluid outside the body cavity. A pump system with two peristaltic hose pumps (double roller pumps) is preferred, one roller pump ensuring the inlet (delivery pump) and the other roller pump ensuring the outlet (suction pump). The system according to the invention also works with several drainage systems.

[0041] The method according to the invention and the device according to the invention can be used in particular with liquid pumps in arthroscopy, urology, hysteroscopy, laparoscopy or for spinal examinations. Furthermore, aspirators can be operated with the method according to the invention and with the device according to the invention.

[0042] Improvements in accordance with the present invention An improvement of the device according to the invention is that the resistance coefficient of every device is stored in the device itself or can be determined by the device itself. For this, it is conceivable, for example, to attach a transponder to each device containing the data. These data can be read by the corresponding transceiver of the pump. The data of the device can directly contain the resistance coefficient. Alternatively, the data of the device can also be identification data, which allows for example to retrieve the resistance coefficient via the Internet from the pump manufacturer. Furthermore, or alternatively, the data can be stored on other media, for example on a multi-dimensionally designable bar code or on a magnetic tape.

Claims

1. 1. A medical device for delivering fluid into a body cavity while determining and controlling an internal pressure during a therapeutic procedure, the medical device comprising: a controllable fluid pump; a delivery flow path; a pressure sensor in the delivery flow path; and a medical device connected to the delivery flow path, the medical device comprising: at least one second flow path for transferring fluid out of the body cavity; Resistance coefficient ζ １ and the resistance coefficient ζ ２ configured to perform a method for determining At least one microprocessor, resistance coefficients ζ of different medical devices ２ and at least one software program, The memory device stores, for each of the different medical devices, a resistance coefficient ζ corresponding to the rate at which fluid is dispensed and the amount of pressure increase and subsequent drop associated with the supply and cessation of the supply of the fluid. ２ I have stored multiple The internal pressure, which is the actual pressure in the body cavity, is estimated based on the pressure measured by the pressure sensor, and the output of the fluid pump is changed to estimate the internal pressure; The resistance coefficient ζ of each of the medical devices １ and the resistance coefficient ζ ２ is the time t at which the fluid pump is stopped after being started ２ A certain time after t ３ It is determined by evaluating the behavior of the pressure measured during Resistance coefficient ζ ２ is assumed to be constant within a particular range of fluid rates and is selected from the memory device based on the amount of pressure rise and fall measured by supplying and stopping the supply of fluid at a constant rate for a predetermined period of time; Resistance coefficient ζ １ is the measurable speed n of the fluid pump １ , the measurable flow pressure p １ , the immeasurable stagnation pressure in the body cavity p ２ , and the resistance coefficient ζ ２ as a function of a predetermined value for [0010] however, n １ If 0, then Equation 1 applies, p １ = Δp + p ２ and Unmeasurable stagnation pressure in the body cavity p ２ is n １ = 0 and time t ≧ t ３ Measurable flow pressure p １ Measured as Δp is n １ >0 and time t=t ２ Measurable flow pressure p １ From n １ = 0 and time t ≧ t ３ Measurable flow pressure p １ It is measured as minus The characteristic curve is determined by the following formula: [0025] The medical apparatus is characterized in that the determined characteristic curve is stored in the memory device of the fluid pump.

2. The medical apparatus for delivering fluid into a body cavity according to claim 1 , characterized in that the medical apparatus is operable with a fluid evacuation device.

3. 3. A medical device for supplying a fluid into a body cavity according to claim 1 or 2, characterized in that said medical device can be used with a liquid pump for arthroscopy, urology, hysteroscopy, laparoscopy or spinal examination.

4. The resistance coefficient ζ １ and ζ ２ 2. The medical device of claim 1, wherein the determination is made by activating the fluid pump twice.

5. The medical device of claim 1 , wherein the fluid is characterized as being a gas or a liquid.

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