JP6666275B2 - Medical pumping equipment - Google Patents

Description

  The present invention relates to medical pump devices, and more specifically to detecting malfunctions in medical pump devices.

  Detecting dysfunction, especially in medical devices, is important because the life of the patient can depend on the proper functioning of the medical device. For example, in the case of an infusion pump, a potentially dangerous consequence caused by the failure is typically an over or under infusion of the drug into the patient.

  Examples of malfunctions include leaks, occlusions, or the presence of air bubbles in the pumping line.

  State-of-the-art devices and methods for detecting malfunctions in medical devices are disclosed, for example, in US Pat.

  When using certain drugs, such as insulin, the detection of occlusion may be particularly important, as it is known that catheters can occlude in numerous environments. Any undetected occlusion can result in underdelivery of insulin because the occlusion remains undetected for an extended period of time. Current occlusion detection devices operate on the piston of the syringe driver and need to generate high pressure in the syringe before the occlusion is detected. Other occlusion detectors consist of a pressure sensor located behind the pump mechanism on the patient's tubing, which is less sensitive, for example, due to tubing line compliance factors. Without the detection of an occlusion when the occlusion begins, the need to increase insulin levels may require a reprogramming of the pump, which occurs when the patient's plasma glucose concentration rises and the occlusion is rapidly released. Large amounts of insulin are administered rapidly and patients may be at serious risk.

U.S. Patent Application Publication No. 2008/214979 European Patent No. 1762263 US Patent No. 7104763

  The present invention provides several further improvements with respect to state-of-the-art devices and methods.

  In the present invention, malfunction detection is based on the measurement of the pressure in the pumping line, and more precisely on the measurement of the pressure in the pumping line between the inlet and the outlet of the pump chamber.

  The above arrangement provides higher sensitivity as well as the ability to detect some types of potential dysfunction.

  More particularly, the invention relates to a medical pump device.

  According to a preferred embodiment of the present invention, the inlet and outlet of the pump device have passive valves. According to a preferred embodiment of the present invention, at least one valve can be further externally controlled.

  Advantageously, and without limitation, highly miniaturized infusion pumps are contemplated within the scope of the present invention. This pump is a membrane pump with two passive valves and is formed using microelectromechanical system technology. Unlike injectable drive pumps, silicon micropumps, preferably micropumps, are formed from silicon and require more complex fluid passages and more precise control of delivery, while potentially exposing the presence of particles. It has a valve with a hard seat that can leak out. Also advantageously, the pump is a micropump having a variable volume of the pump chamber, consisting of 10 nl to 10 μl.

  In a further preferred embodiment of the present invention, a pressure sensor having a silicon film is used.

  In another advantageous embodiment of the invention, the pressure sensor is arranged between the pump chamber and the outlet. This arrangement handles other purposes, such as malfunction detection, while more accurately controlling occlusions (including the possibility of directly detecting the onset of occlusion during any pumping cycle).

  According to another preferred embodiment of the present invention, the system comprises a further pressure sensor.

  This further pressure sensor can preferably be arranged after the outlet valve in the downstream line. Further, the pump device includes a flow restrictor in the downstream line. Also, this additional pressure sensor is positioned between the outlet valve and the flow restrictor.

  In some embodiments, the system further comprises a temperature sensor.

  The pressure sensor of the present invention can generally detect some types of malfunctions, such as blockages, air bubbles, disconnection of the infusion line, etc. in a very short time, i.e. seconds, when the pump is running. .

  It is another object of the present invention to accurately characterize the pump and / or monitor the characteristics of the pump during the manufacturing cycle to prevent any potential malfunction during use.

  The purpose of manufacturing any medical device is to ensure the quality of each pump delivered to the patient. For any of the above medical products, the use of liquid is generally the only way to detect pump malfunction. The above test requires a long time, a considerable cost, and is only possible if the entire fluid line is changed after the above test. In the case of single use products (such as disposable pumps), the fluid line cannot be changed and therefore it is not possible to test each of the above pumps manufactured due to contamination of the liquid during the test It is. Therefore, a single sampling was run, and the test does not guarantee 100% quality control and is considered destructive to the pump.

  The present invention further provides a system and method for fully controlling each manufactured pump without causing contamination of the pump. The test described above is preferably realized with sterile air and performs a detailed analysis of all the important parameters and safety properties in a very short time of only a few seconds. This method is compatible with the cost goals of the disposable pump described above, which must be very inexpensive to manufacture.

  The invention will be better understood in the following using a detailed description, including the examples shown in the following figures.

1 shows a cross-sectional view of a micropump according to a preferred embodiment of the present invention. Fig. 4 shows possible steps for a functional test of the pump. Fig. 4 shows possible steps for a functional test of the pump. Fig. 4 shows another pressure characteristic of a function test indicating dysfunction. Figure 4 shows typical pressure characteristics during a working cycle. Fig. 2 shows a working cycle of one preferred embodiment. Figure 3 shows an air and water pumping cycle. Fig. 4 shows a typical evolution of the outlet pressure profile when there is an obstruction. Fig. 4 shows a typical evolution of the inlet pressure profile when there is an obstruction. 9 shows an example of monitoring the outlet pressure during occlusion. The pressure characteristic of the pump when there is a leak is shown. 7 illustrates monitoring the accuracy of the pump when the flow rate is decreasing. The relative change in viscosity is shown for a temperature change of 1 ° C. The words "vertex" and "horizontal area" indicate the method used in the figure.

  The micropump 1 shown in FIG. 1 is extremely miniaturized and is a reciprocating membrane pump mechanism. The micropump 1 is made of silicon and glass using a technique called MEMS (microelectromechanical system). The micropump 1 has an inlet control member, in this embodiment an inlet valve 2, a pump member 3, a function detector 4 capable of detecting various defects in the system, and an outlet valve 5. The principle of the above micropump is known, for example, in US Pat. No. 5,759,014.

  FIG. 1 shows a glass layer (blue) as a substrate 8, a silicon layer (purple) as a second plate 9 fixed to the substrate 8, and an upper plate as a second plate 9 fixed to the silicon plate 9. A pump having a second glass layer 10 (blue) deposited thereon and defining a pump chamber 11 having a volume is shown.

  The pump member can be controlled and displaced by an actuator (not shown in the present specification) connected to the mesa unit 6. In addition, a passage 7 exists for connecting the outlet valve 5, which is an outlet control member, to an outlet port located on the opposite side of the pump.

Principle of the Detector In the pump 1, the pressure in the pump chamber varies during the pumping cycle, such as the operating speed, the pressure at the inlet, the pressure at the outlet, the potential presence of bubble volume, the characteristics of the valve and the leak rate of the valve. Will change depending on the factors.

  According to the invention, the aim is to monitor this pressure and analyze the contour from one stroke to another in order to detect a potential malfunction.

Integrated pressure sensor The pressure sensor 4 in the micropump 1 is made of a silicon membrane located between the pump chamber and the outlet of the pump. This pressure sensor 4 is located in a passage formed between the surface of the silicon layer of the micropump and the glass layer on the upper surface thereof. Further, the pressure sensor 4 includes a set of strain sensing resistors in a Wheatstone bridge configuration on the membrane, utilizing the giant piezoresistive effect of silicon. The change in pressure induces membrane distortion and therefore the bridge becomes unbalanced. Pressure sensors are designed to produce a signal that is linear with pressure within the typical pressure range of the pump.

  Fluid is in contact with the surfaces of the interconnect leads and the piezoresistors. Good electrical insulation of the bridge is ensured by using a further surface doping of a polarity opposite to that of the leads and the piezoresistors.

  In another preferred embodiment of the invention, the pressure sensor comprises an optical sensor. This sensor is preferably arranged between the two valves, one component contained in the path of the pump and outside the said fluid passage, which can measure the pressure inside the fluid passage. And at least some optical components. In another embodiment, the optical detector can be located completely inside the pump to measure the pressure between two valves in the fluid passage. In another embodiment, the astigmatic element is located in the optical path, ie between the flexible membrane and the optical sensor in the pump. Any change in pressure within the pump will induce a displacement of the membrane, a change in the optical path, and a change in the shape of the light beam caused by the presence of this astigmatic element. The optical sensor preferably senses the shape of the light beam, for example by having a codrant photodetector.

Functional Test The first step of the invention that can be performed with a pump is, for example, a functional test of the pump at the manufacturing level.

  Known functional tests using water last several hours and are considered harmful, while functional tests using the pump of the present invention can be performed in seconds using only gas. This uses a small dead volume of the pump for this test and the integrated pressure sensor described above.

The principle of the functional test process is as follows.
Excessive pressure is created inside the pump with the actuator, and the user monitors the pressure decay in the pump chamber, which is a direct indication of the leak rate. The maximum pressure is related to the compression ratio of the pump and the capacity of the self-priming type. The user can also pull out the pretension of the valve during a typical working cycle.

  To create high pressure in the pumping chamber, the user can control the outlet valve, for example, pneumatically, so as to keep the outlet valve closed during compression as shown in FIGS.

In particular, FIGS. 2 and 3 show a functional test of the pump of the invention (FIG. 2 shows a schematic process and FIG. 3 shows the corresponding pressure characteristics).
During this test, the user monitors the detector signal by:
A zero pressure indicates a rest position of the membrane.
The peak of pressure indicates the compression ratio of the micropump,
Pressure decay indicates the leak rate of the valve,
The pressure in step 3 indicates the pretension of the outlet valve,
The pressure in step 4 indicates the pretension of the inlet valve.

  As shown (eg, in the continuous position of FIG. 2), the test is started from a standby position. First, a pulling step of “sucking” gas from the inlet valve 2 into the chamber is performed by moving the membrane 3.

  This is followed by a push step to empty the chamber with gas and the outlet valve 5 is open. In the next step, the outlet valve 5 closes again and performs a further pulling step on the membrane 3, then in the next step the user opens the outlet valve 5 and relaxes the pressure in the chamber.

  Finally, the outlet valve 5 is closed and the user performs a pushing step on the membrane 3 corresponding to a compression step. At this time, the chamber is under high pressure and the pressure decay (see FIG. 3) indicates the leak rate of the valve.

  The sensitivity of the above method is very high due to the high pressure generated and the associated small volume.

  A direct correlation between compression ratio and stroke volume SV, given that the dead volume DV does not change too much by appropriate process control (eg, microelectromechanical system technology) during the initial manufacture of the pump. Is found.

  FIG. 4 shows a pressure characteristic when a defect is present in the function test.

  In this case, the inlet valve of the pump is joined (maintained closed) and there is further leakage. These problems with the inlet valve can be elicited by the large pressurization that occurs during the pushing movement of the pump and the reduced pressure decay after each actuation. Leakage is indicated by a pressure decay at the end of the test cycle, at the end of the high compression step.

  The same applies when the fluid from the drug reservoir located in front of the first valve (e.g. at the end of the reservoir) is depleted, especially when using a non-vented, soft reservoir that is closed and during operation of the pump. The result is obtained.

In-line dysfunction detection As described above, the pressure in the pumping chamber during fluid operation is determined not only by the inlet or outlet pressure, operating characteristics, but also by the tightness of the valve, the actual stroke volume or the pressure of the valve. It depends on various functional and / or external parameters such as the characteristics of the micropump such as tension.

  A typical pressure profile during a working cycle with liquid is shown in FIG.

  Changes in this characteristic can be caused by pump malfunction or ingress or egress pressure (e.g., due to poor ventilation, under or over pressure of the liquid reservoir located in front of the inlet valve, or blockage after the outlet valve). Indicates an increase or decrease.

  In particular, the position of the plateau just after the first peak of the measured pressure in the pump chamber is directly indicative of the pressure at the outlet of the pump, after the outlet valve. After the second apex, the user gets a direct indication of the pressure at the inlet, before the inlet valve. The tightness of the valve and / or the presence of air bubbles induces a change in peak-to-peak amplitude and a peak width. Analysis of the pressure decay after each peak of pressure indicates the leak rate of the valve.

  The displacement of the membrane of one embodiment of the invention during a normal operating cycle of the pump is shown in FIG.

  According to the exemplary embodiment described above, the working cycle is initiated by a first pushing movement of the membrane, which results in an increase in pressure, opening of the outlet valve and draining of the liquid. The working cycle is followed by a full pull stroke to fill the pump (negative peak of pressure during filling of the pump), then the pumping membrane is released, thus returning to its standby position, Induce a second positive vertex.

  As mentioned above, the gradual change in pressure in the pump chamber depends directly on the operating characteristics of the membrane.

  For example, it is possible to have a cycle that begins with a full stroke, resulting from a full pull motion, followed by a full push motion. The above cycle is typically useful during rapid operation of the pump, for example, during a bolus dose. In a similar operation, only two vertices, the first negative and the positive, can be measured. This analysis can be correlated with operating characteristics, resulting in the detection of the same type of malfunction.

As a result, the following features can always be measured during the pumping cycle using the pressure signal from the sensor located between the two valves, and directly exhibit the following characteristics:
1. The position of the horizontal area immediately after the positive peak (+) of the pressure depends on the pretension of the outlet valve and the pressure at the outlet of the pump after the outlet valve.
2. The position of the horizontal area immediately after the negative peak of pressure (-) depends on the pretension of the inlet valve and the pressure at the pump inlet before the inlet valve.
3. The tightness of the valve and hence the leak correlates with a damping having a time of pressure after each peak.
4. The relative position of the two horizon also has a direct correlation with the leak rate.
5. The height and width of the pressure (positive or negative) apex correlates with the presence of air in the pump.

Priming and Air Detection Pump priming can also be monitored. Significant differences in the monitored signals while pumping air and water are shown in FIG.

  As described above, the peak of pressure has been modified by the presence of air in the pump.

Hereinafter, the detection of air can be verified by:
1) monitoring the height of the pressure peak, which can be a warning at a predetermined threshold,
2) monitor the width of the pressure peak, which can be a warning at a predetermined threshold,
3) Monitor the height and width (e.g., via signal integration), which will be the determined alert threshold.

Outlet Pressure Monitoring FIG. 8 shows a typical evolution of the pressure profile during operation when there is pressure at the outlet of the pump after the outlet valve.

Inlet Pressure Monitoring FIG. 9 is a graph similar to FIG. 8, showing a typical evolution of the pressure profile during operation when there is pressure at the inlet.

  Thus, accurate monitoring of both the inlet pressure and the outlet pressure during the working cycle is obtained.

  If the reservoir is, for example, a soft reservoir with no vent, monitoring the inlet pressure can help detect that the drug reservoir is empty.

Blockage Detection By monitoring the outlet pressure, blockage can be detected as shown in FIG.

  During occlusion, there are several ways to analyze the curve reproduced in FIG. For example, the pressure profile can simply be observed after each pushing movement.

Blockage detection can be performed as follows.
1) Typically, when the horizon (+) position is equal to the initial height of the vertex (+), monitor the horizon (+) position and the established warning threshold.
2) Monitor the warning threshold and the height and width of the vertex (+).

  Because the pressure measurement in the pump is made in the fluid passage and correlated with other measurements indicating other potential malfunctions, the pressure measurement in the pump described Accurate and precise detection. Therefore, the measured result value can be correlated to a true occlusion or fluid restriction outside the pump, preventing the patient from notifying the need to check the infusion line or change the injection site.

Leak Detection FIG. 11 shows the pressure characteristics of the pump when there is a leak. After each actuation, the pressure relaxes very quickly to external pressure. If there is a leak, the pressure should relax to valve pretension, expressed in units of pressure.

  Therefore, leakage can be detected by the detection method of the present invention while preventing free flow by the pretension of the valve.

According to the notation shown in FIG. 14, the detection of leakage can be performed as follows.
1) The relative positions of the horizontal area (+) and the horizontal area (-) and the determined warning threshold are monitored.
2) Monitor the pressure lag after each peak of pressure and a defined alert, typically using a time constant.

Monitoring Pump Accuracy in Closed Loop Applications, For example, Insulin According to the present invention, a user can detect defects, such as valve leaks and air bubbles, that can perform pump accuracy within accuracy specifications.

  FIG. 12 shows an example of a pump showing a nominal stroke volume and a detector signal of the same pump with particles implementing 15% pumping accuracy. Leakage induced by these particles can be easily detected by analyzing the level difference before and after the large negative peak.

  This feature allows closed-loop applications by coupling a micropump to a glucometer, with control of insulin delivery accuracy via a detector.

Here, detection is similar to leak detection, but the only focus is on leaks that affect accuracy.
1) Determine the relative position of the horizon (+) and horizon (-), typically when their positions are equal after a typical time constant immediately after the vertices (+) and (-) Monitor the warning threshold that has been set.
2) Monitor the pressure lag after each peak of pressure and fixed alerts, typically using a time constant.

  In the absence of close monitoring of the pump accuracy, any of the above closed-loop systems can be used with the measured parameters (in the above case, for example, in the case of plasma or blood glucose in the subcutaneous area) without taking into account changes in pump delivery. Or monitoring interstitial fluid continuously), eg, increasing or decreasing the administration of insulin. In the case of a closed loop system, it is most important to ensure that the pumping parameters are well understood and controlled over time to prevent any false compensation that may be related to the pumping mechanism and not related to the patient's characteristics. is there. In particular, over-infusion of insulin due to increased glucose readings can potentially jeopardize the patient when it concerns an unknown defective pump or infusion set. This is especially true where glucose measurements indicate glucose plasma levels within a delay of 10-30 minutes. In the above case, the faulty pump will misinterpret the patient's condition, while preventing the misinterpretation from putting the patient at risk, such as by obstructing the infusion line from obstruction. Any modification (removal or modification of the pumping properties) will not be detected over time.

Detection of Infusion Line Disconnection In some instances, the infusion line is disconnected from the pump, and leakage may occur between the pump outlet and the infusion line connector. Leaks can also be present when a user connects an unauthorized infusion line to the pump outlet. This reduces the fluid resistance at the pump outlet due to the leakage. A small decrease in pressure at the pump outlet when leakage is significant can be detected by using an integrated detector or by placing a second pressure sensor in the micropump and after the outlet valve. . The sensitivity of this sensor, under standard conditions, must be adapted to the pressure drop in the injection line.

  A high instantaneous flow rate of the pump, due to the working principle of the pump, is very favorable, since the pressure drop in the injection line is directly proportional to the flow rate.

  If necessary, preferably before the patient is connected (e.g., during priming of the pump), during the draining of the liquid during the setting of the pump, e.g. by creating a stroke at a higher speed, the infusion line A specific test of air tightness can be performed.

A further pressure sensor at the outlet of the pump A main detector is located in the pump chamber. As long as the pump system is well ventilated, its reference port communicates with the air space in the housing of the pump system, which is at atmospheric pressure. This sensor is furthermore an associated pressure sensor. It may be useful to obtain information about the patient's pressure by placing an additional pressure sensor after the outlet valve.

  This additional pressure sensor is directly related to the patient's pressure. The two pressure sensors, the main pressure sensor measuring the pressure in the pump chamber and the pressure sensor measuring the pressure after the outlet valve, should have the same reference port pressure. Comparing the development of the two signals after the stroke can be a leak in the pump at the valve seat or a leak between the outlet port of the pump (typically due to poor connection of the set of patients) and the patient. Useful for detection. This is described in further detail herein.

  In addition, the pressure difference between the two sensors immediately after the stroke, i.e. when there is no flow, also indicates the tightness of the outlet valve.

  This additional sensor can also be used to detect abnormal pressure at the outlet port, including occlusion of the infusion set.

  This additional sensor can also be calibrated during a feature manufacturing test, if desired, using the gases described herein above.

  This additional pressure sensor can be easily integrated into the pump tip by designing a second membrane for pressure measurement. This pressure can be measured by using a strain gauge in a Wheatstone bridge configuration used as another pressure sensor in the pump. Ideally, the injection dose for the strain gauge is equivalent to those of the main detector in the pump. Therefore, the user can adjust the sensitivity, if necessary, by simply modifying the dimensions of the membrane, rather than the dose itself.

  The fluid passage between the pump outlet valve and the patient set should preferably be made so as not to trap air during the initial pump priming.

Implementation of a Temperature Sensor for Better Leakage and Monitoring Accuracy Using Additional Pressure Sensors This section describes the reliability of the second detection signal during analysis.

  As mentioned above, the width and height of the pressure peak can be used to obtain information about the tightness of the downstream line between the pump and the patient. The user can also propose qualitative criteria for these different features.

Further, the integral of the pressure versus time curve is theoretically proportional to flow for a given fluid resistance. This change in integration is a good indication of malfunctions, including temperature changes as well as bubbles and leaks.
P (t) -P (patient) = Rf × Q (t)
Where Rf is the fluid resistance between the further pressure sensor and the patient, Q (t) is the instantaneous flow rate, and P (t) is the pressure measured by the further sensor.
Considering laminar flow, Rf is given by Poiseuille's law.
P (patient) is the pressure of the patient and also the pressure measured by a further sensor after the flow has ceased.

  This sensor also provides a good indication of pump accuracy as it has direct access over time for flow changes. Of course, for a given pumping system with an infusion set, the fluid resistance varies with temperature through fluid viscosity (Poiseuille's law). Ideally, this pressure sensor is also connected to a temperature sensor.

  If a fluid such as water is used, the change in viscosity with temperature is known and the signal can be corrected so that it is not temperature dependent. Failure detection becomes more reliable.

  Even if the temperature sensor is not strictly necessary due to the small dimensions and good heat conduction of the pump components, the temperature sensor can be located in the pump, for example in contact with a fluid.

  The thermal sensor can be a simple thermal resistor (RTD or resistance temperature detector) that shows good sensitivity between 5 and 40 ° C. The Wheatstone bridge of the pressure sensor also exhibits a similar temperature dependence and may serve for this purpose. Thermocouples can also be incorporated in the pumping unit. Finally, a semiconductor temperature sensor based on the basic temperature and current characteristics of a diode or transistor can be used.

  If two identical transistors are operated at different but constant collector current densities, the base-emitter voltage difference is proportional to the absolute temperature of the transistor. This voltage difference is converted to a single-ended voltage or current. An offset may be applied to convert the signal from absolute temperature to degrees Celsius or Fahrenheit.

  FIG. 13 shows the relative change in viscosity for a 1 ° C. temperature change. Fluid resistance varies linearly with viscosity, allowing direct access to flow rate accuracy, which can be expected for a 1 ° C. temperature sensor resolution. At 5 ° C., the maximum error induced by the temperature sensor for flow accuracy is 2.8%. Temperature sensors can also be designed to induce errors below the accuracy target for the flow rate.

  The combination of the outlet pressure sensor and the temperature sensor can be used as a sophisticated related pulsed flow sensor that is efficient due to the small response time of the pressure sensor.

Absolute flow meter For absolute flow measurement, the fluid resistance between the additional pressure sensor and the patient should be known to have good accuracy. The patient set shows typically a large change in fluid resistance from one batch to another compared to the fluid resistance of the passages in the micropump. Care should also be taken to keep the fluid resistance of the set of patients very low compared to the fluid resistance of the outlet passage in the micropump.

  The above-described fluid resistance Rf can be controlled with an accuracy compatible with absolute flow rate measurement.

  According to the above description, the fluid measurement is effective as long as the fluid resistance of the set of patients is small, that is, as long as the fluid line is not blocked.

  The flow rate at the outlet of the micropump is measured. Any leakage after an additional pressure sensor (such as a connector) will induce a change in the signal shape of both detectors, but the fluid measurement will remain accurate.

  Fluid monitoring is also a very powerful feature, but accurate interpretation of flow data requires information from both detectors.

During further pressure sensor calibration, it is also possible to calibrate the integral of the pressure signal proportional to the flow rate (typically by using a commercial flow meter placed in series with the pump outlet). is there. Here, care must be taken during the test not to cause a large fluid resistance at the outlet.

  Of course, the invention is not limited to the examples described and illustrated above, but extends to any embodiment falling within the scope of the appended claims.

Claims (12)

In a method for performing a functional test of a medical pump device,
Providing a medical pump device comprising a pressure sensor, a pump chamber having a variable volume, an inlet having a passive valve, and an outlet having a passive valve;
Providing a test fluid used to perform the functional test, the test fluid being different from the fluid used in normal operation of the pump;
Generating pressure in the pump chamber;
Monitoring the pressure signal sent by the pressure sensor;
A method for performing a functional test of a medical pump device, wherein the passive valve at the outlet is controlled by external means during at least part of the functional test.   The method of claim 1, wherein the pressure signal is monitored at least in a step of generating pressure in the pump chamber.   The method of claim 1, wherein the pressure signal is monitored at least when the pump chamber is under high pressure.   The method of claim 1, wherein generating pressure in the pump chamber is performed by changing a volume of the pump chamber.   The method of claim 1, wherein the test fluid is a gas and the working fluid is a liquid.   The method of claim 1, wherein the outlet passive valve is kept closed for at least a portion of the functional test.   The method of claim 1, wherein the outlet passive valve is kept closed at least during a step of generating pressure in the pump chamber.   2. The method of claim 1, further comprising monitoring a pressure peak to determine a compression ratio.   The method of claim 1, further comprising monitoring a pressure decay by a processor to determine a leakage rate of the pumping chamber and / or fluid passage.   The method of claim 1, further comprising monitoring a pressure characteristic by a processor to determine a pretension of at least one passive valve of the inlet passive valve and the outlet passive valve.   The method of claim 1, further comprising monitoring pressure characteristics to determine whether at least one of the inlet passive valve and the outlet passive valve is joined. Method.   The method according to claim 1, wherein the pressure sensor is located within the pump chamber.

Images