METHOD FOR ASCERTAINING THE VERTICAL DISTANCE BETWEEN A PATIENT (LEVEL OF SURGICAL INTERVENTION) AND A FLUID DELIVERY PUMP

Abstract

Subject matter of the invention is a method for determining the difference in height level between a medical fluid pump and the body cavity of a patient for the correction of the measurement of the fluid pressure existing at the outlet end.

Claims

1. A method for determining the difference in height level h.sub.pat between a patient (10) and a fluid feed pump (5) with a current sensor (12) and with a bidirectional pressure sensor (6) in a tube section (7) between fluid feed pump (5) and connection to a connector (8) or an instrument (9), comprising a reservoir (1) of a medical device arranged above the fluid feed pump (5), the fluidic connection paths being placed in the devices according to the application, being, however, still unfilled, and the volume of the fluidic connection paths being known, characterized by the following steps: a) fluid feeding by the fluid feed pump (5) with a transport roller wheel (4) through the through-going fluidic connection of the reservoir (1), b) stop of feeding, as soon as the pressure sensor (6) detects a change in pressure, which is caused by the fed water column, c) backward rotation of the transport roller wheel (4) while measuring, by the current sensor (12), the motor current required for feeding from the tube section (3) to the reservoir (1), d) calculation of the pressure value P.sub.wat at the patient from the required motor current, e) continuation of the tube and instrument filling process, until the tube section (7) is completely filled, f) detection of the fluid exit from the open end of the tube section (7) or instrument (9) by evaluation of the pressure values at the pressure sensor (6), g) termination of the filling phase/feeding, h) evaluation of the pressure value P.sub.hyd of the pressure sensor (6), i) use of the pressure value P.sub.hyd for the determination of the difference in height level h.sub.pat between the transport roller wheel (4) and patient (10), wherein a positive pressure value P.sub.hyd indicates that the pump (5) is below the height level of the patient (10), a negative pressure value P.sub.hyd indicates that the pump (5) is above the height level of the patient (10), a pressure value P.sub.hyd 0 (zero) indicates that the pump (5) is at the height level of the patient (10).

2. A method for determining the difference in height level h.sub.pat between a patient (10) and a fluid feed pump (5) with a current sensor (12) and with a unidirectional pressure sensor (6) in a tube section (7) between fluid feed pump (5) and connection to a connector (8) or an instrument (9), comprising a reservoir (1) of a medical device arranged above the fluid feed pump (5), the fluidic connection paths being placed in the devices according to the application, being, however, still unfilled, and the volume of the fluidic connection paths being known, characterized by the following steps: a) fluid feeding by the fluid feed pump (5) with a transport roller wheel (4) through the through-going fluidic connection of the reservoir (1), b) stop of feeding, as soon as the pressure sensor (6) detects a change in pressure, which is caused by the fed water column, c) backward rotation of the transport roller wheel (4) while measuring, by the current sensor (12), the motor current required for feeding from the tube section (3) to the reservoir (1), d) calculation of the pressure value P.sub.wat at the patient from the required motor current, e) continuation of the tube and instrument filling process, until the tube section (7) is completely filled, f) detection of the fluid exit from the open end of the tube section (7) or instrument (9) by evaluation of the pressure values at the pressure sensor (6), g) termination of the filling phase/feeding, h) evaluation of the pressure value P.sub.hyd of the pressure sensor (6), i) use of the positive pressure value P.sub.hyd for the determination of the difference in height level h.sub.pat between the transport roller wheel (4) and patient (10), wherein a positive pressure value P.sub.hyd indicates that the pump (5) is below the height level of the patient (10), a pressure value P.sub.hyd 0 (zero) indicates that the pump (5) is at the height level of the patient (10) or above the height level of the patient (10), j) in the case of a pressure value P.sub.hyd 0 (zero), backward feeding of the fluid by backward rotation of the transport roller wheel (4), k) determination of the motor current by evaluation of the current sensor (12) and calculation of the pressure for the determination of the height level between the transport roller wheel (4) and the height of patient (10), the pump (5) being below the height level of the patient (10).

3. A method for determining the difference in height level h.sub.pat between a patient (10) and a fluid feed pump (5) with a current sensor (12) and with a bidirectional pressure sensor (6) in the tube section (7) between fluid feed pump (5) and connection to a connector (8) or instrument (9), and with another pressure sensor (11) between a reservoir (1) and the transport roller wheel (4) with the reservoir (1) of a medical device being arranged above the fluid feed pump (5), wherein the fluidic connection paths are placed in the devices according to the application, being, however, still unfilled, and the volume of the fluidic connection paths being known, characterized by the following steps: a) fluid feeding by the fluid feed pump (5) with a transport roller wheel (4) through the through-going fluidic connection of the reservoir (1) to the roller wheel, b) stop of feeding, as soon as the pressure sensor (6) detects a change in pressure, which is caused by the fed water column, e) reading the pressure value P.sub.wat at the pressure sensor (11), d) continuation of the tube and instrument filling process, until the tube section (7) is completely filled, e) detection of the fluid exit from the open end of the tube section (7) or instrument (9) by evaluation of the pressure values at the pressure sensor (6) f) termination of the filling phase/feeding, g) evaluation of the pressure value P.sub.hyd of the pressure sensor (6), h) use of the pressure value P.sub.hyd for the determination of the difference in height level h.sub.pat between the transport roller wheel (4) and patient (10), wherein a positive pressure value P.sub.hyd indicates that the pump (5) is below the height level of the patient (10), a negative pressure value P.sub.hyd indicates that the pump (5) is above the height level of the patient (10), a pressure value P.sub.hyd 0 (zero) indicates that the pump (5) is at the height level of the patient (10).

4. A method for the determination of the difference in height level h.sub.pat between a patient (10) and a fluid feed pump (5) with a current sensor (12) and with a unidirectional pressure sensor (6) in the tube section (7) between fluid feed pump (5) and connection to a connector (8) or instrument (9), and with another pressure sensor (11) between a reservoir (1) and the transport roller wheel (4), with the reservoir (1) of a medical device being arranged above the fluid feed pump (5), the fluidic connection paths being placed in the devices according to the application, being, however, still unfilled, and the volume of the fluidic connection paths being known, characterized by the following steps: a) fluid feeding by the fluid feed pump (5) with a transport roller wheel (4) through the through-going fluidic connection of the reservoir (1) b) stop of feeding, as soon as the pressure sensor (6) detects a change in pressure, which is caused by the fed water column, c) reading the pressure value P.sub.wat at the pressure sensor (11), d) continuation of the tube and instrument filling process, until the tube section (7) is completely filled, e) detection of the fluid exit from the open end of the tube section (7) or instrument (9) by evaluation of the pressure values at the pressure sensor (6), f) termination of the filling phase/feeding, g) evaluation of the pressure value P.sub.hyd of the pressure sensor (6), h) use of the positive pressure value P.sub.hyd for the determination of the difference in height level h.sub.pat between the transport roller wheel (4) and patient (10), wherein a positive pressure value P.sub.hyd indicates that the pump (5) is below the height level of the patient (10), a pressure value P.sub.hyd 0 (zero) indicates that the pump (5) is at the height level of the patient (10) or above the height level of the patient (10), i) in the case of a pressure value P.sub.hyd 0 (zero) backward feeding of the fluid by backward rotation of the transport roller wheel (4), j) determination of the motor current by evaluation of the current sensor (12) and calculation of the pressure for the determination of the height level between the transport roller wheel (4) and the height level of the patient (10), wherein the pump (5) is below the height level of the patient (10).

5. The method according to claim 1, wherein the detection of the proper exit of the fluid through the transport tube (7) and the medical instrument (9) in the cavity of the patient (10) is performed by the following steps: a) fluid feeding by the pump (5), until a pressure value different from zero is indicated at the pressure sensor (6), b) further fluid feeding, until the fed volume is larger than the volume of the tube, with the pressure measured at the pressure sensor (6) remaining constant, c) detection of a pressure increase at the pressure sensor (6) after feeding a liquid volume, which is larger than the volume of the tube.

6. The method according to claim 1, wherein the detection of a faultily closed valve (8) is performed by the following steps: a) fluid feeding by the pump (5), until a pressure value different from zero is indicated at the pressure sensor (6), b) further fluid feeding, wherein the pressure measured at the pressure sensor (6) significantly increases, before the fed volume corresponds to the volume of the tube.

7. The method according to claim 1, wherein the detection of the instrument faultily not being in the body cavity or of a non-closed connection between transport tube (7) and medical instrument (9) is performed by the following steps: a) fluid feeding by the pump (5), until a pressure value different from zero is indicated at the pressure sensor (6) b) further fluid feeding, until the fed volume is larger than the volume of the tube, with the pressure measured at the pressure sensor (6) remaining constant, c) detection that after feeding a liquid volume, which is larger than the volume of the tube, no pressure increase is measured at the pressure sensor (6).

8. The method according to claim 1, wherein the volume of the fluidic connection paths of the pump is read out from an information carrier provided at the tube set prior to starting the process.

9. The method according to claim 8, characterized by that the information carrier is an RFID-Chip, a magnetic tape, a barcode or an EPROM.

10. A method for determining the hydrostatic pressure of a fluid feeding device comprising a medical fluid feed pump (5), wherein the roller wheel of the pump is rotated against the feeding direction, wherein the current required for the transport against the feeding direction is measured by current sensors (12), and wherein the measured current is taken as a measure for the hydrostatic pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0042] The solution according to the invention for the determination of the patient's height level h.sub.pat that causes a hydrostatic pressure (P.sub.hyd), must differentiate between two cases: [0043] I) The patient (surgery area) (10) is at a higher level than the pressure sensor (6) of the pump (5) (h.sub.pat>0) (FIGS. 1 and 2). [0044] II) The patient (surgery area) (10) is at a lower level than the pressure sensor (6) of the pump (5) (h.sub.pat<0) (FIG. 3).

[0045] It is assumed, herein, that between the pressure sensor (6) and the hydraulically effective height of the transport roller wheel (4), there is no relevant difference in height. A value for ‘no relevant difference in height’ is 3 cm water column.

[0046] Further, there are different cases of the procedure: [0047] a) An employed instrument (9) is outside of the patient (10) or the cavity of the surgery area, and the outlet end is open to the ambient atmosphere or to ambient pressure. [0048] b) The employed instrument (9) has already been introduced into the cavity of the surgery area, and there acts a (higher and unknown) cavity pressure P.sub.cav at the outlet end. [0049] c) The outlet valve (8) in the fluid connection is closed, or the tube section (7) is disconnected.

[0050] In the case I), a), a fluid of the pump (5) is fed from the reservoir (1), in order to fill the tube (3, 7) and the instrument (9) with the fluid. The pressure at the sensor (6) reaches a stationary value, i.e., it changes in its mean value in the lower single-figure percentage range only, when the tube (3, 7) and the instrument (9) are filled up. In this case, the pump (5) is stopped. The stationary pressure value (P.sub.drv) measured after the stop of the pump (5) corresponds to the hydrostatic pressure (P.sub.hyd). By the static deduction of the value P.sub.hyd from the sensor value P.sub.drv, the hydrostatic pressure (P.sub.hyd) is thus compensated.

[0051] In the case II), a), a fluid of the pump (5) is fed from the reservoir (1), in order to fill the tube (3, 7) and the instrument (9). The pressure at the sensor (6) reaches a stationary value, when the tube (3, 7) and the instrument (9) are filled up. In this case, the pump (5) is stopped. The measured stationary pressure value (P.sub.drv) corresponds to the hydrostatic pressure (P.sub.hyd), when a bidirectional pressure sensor is used that can measure positive and negative pressures relative to ambient pressure. In this case, the static value P.sub.hyd can be added to the sensor value P.sub.drv, in order to determine the hydrostatic pressure (P.sub.hyd) in the cavity and to compensate the measurement error.

[0052] In order to determine, in the case II), a), the hydrostatic pressure (P.sub.hyd) by means of a unidirectional sensor, the method has to be extended. A unidirectional sensor can only measure values above ambient pressure, that is, positive values. After the tube (3, 7) and the instrument (9) have been filled with a liquid, and the pressure sensor (6) determines a stationary measurement value, the pump (5) is stopped. Then, the pump (5) is operated in the opposite feeding direction, and draws in the fluid in the tube section (7). By means of torque measurement of the pump motor, the necessary force or, under consideration of the inner diameter of the tube, the draw-in pressure (P.sub.m) at the pump (5) can be deducted. Herein is torque—force pressure. The determination of the torque may be made by measurement of the motor current of the transport roller wheel (4) of the pump (5). When the necessary draw-in pressure is known, at which the fluid from the tube (3, 7) and instrument (9) is fed back, the hydrostatic pressure (P.sub.hyd) can be calculated thereby. This requires the knowledge in advance, how high the hydrostatic pressure P.sub.wat from the reservoir (1) to the pump level is. The calculation is made as per:

P.sub.m−P.sub.wat=P.sub.hyd.

[0053] When the hydrostatic pressure P.sub.wat of the reservoir (1) is to be measured, there are two possibilities: First, the use of a second pressure sensor (11) between the transport roller wheel (4) and the reservoir (1). Second, a determination by measurement of the pressure P.sub.wat via the torque measurement of the fluid feed pump (5). In the second case, an initial measurement process is needed, before the hydrostatic pressure (P.sub.hyd) in the tube section (7) and the instrument (9) can be determined. The pump (5) is started with no fluid in the tubes, in order to feed the fluid from the reservoir (1) into the tube section (3). At that moment, when the fluid reaches the transport roller wheel (4) or the location of the pressure sensor (6), and water is fed into the tube section (7) between pump (5) and patient (10), a pressure increase is detected at the pressure sensor (6). The pump (5) is stopped, and the feeding direction is changed (pump (5) feeds the fluid back to the reservoir (1), in the tube section (7) between pump (5) and patient (10) there is no significant amount of fluid). The necessary motor torque of the pump (5), in order to feed the fluid from the tube section (7) into the tube section (3) between reservoir (1) and pump (5), is proportional to the pressure P.sub.wat, and the coefficient of proportionality can be determined previously by measurement for the employed inner diameter of the tube section (3). The procedure in this regard would be a previous measurement of the correlations and when putting the pump (5) into operation, an assignment of the coefficient of proportionality depending on the detected tube set. The detection and transmission of data may take place, e.g., by means of an RFID chip in the tube set.

[0054] In an alternative embodiment, from the inner diameter of the tube or the area of the tube cross-section in the tube section (3) calculated therefrom and motor torque, the pressure P.sub.wat and thus the height level between the transport roller wheel (4) and the fluid level in the reservoir (1) can mathematically be determined:

P.sub.wat=(motor torque)/(radius of the transport

roller wheel(4).Math.area of the tube cross-section

in the tube section(3))

[0055] In the case I) b) and the case II) b), the methods from case I) a) and case II) a) can be used in a modified manner. First, the tube section (7) between pump (5) and patient (10) and the instrument (9) is filled via the pump (5) with a fluid, until the pressure at the sensor (6) becomes stationary. When the instrument (9) is introduced into a closed cavity in the patient (10) (see FIG. 4, point of time to), the pressure will continue to increase and will not reach a stationary value, as long as the pump (5) feeds a fluid (FIG. 4, curve with flow (volume flow) q=constant). From this detected course of the pressure signal, it can be concluded that case I) b) and case II) b) are present. In this case, the pressure value at the sensor (6) at the point of time to is assigned as hydrostatic pressure P.sub.wat.

[0056] If a unidirectional pressure sensor should be employed, the pump must be stopped at the point of time to, and the method described above under case II), a) should be performed, in order to calculate the hydrostatic pressure P.sub.wat.

[0057] In the case I) c) and the case II) c), at first, no values can be determined. Prior to the use of the device and thus prior to the necessity to use a height detection for the compensation, a situation according to the case a) will occur, since the user has confirmed that the tube is filled and correspondingly the height detection will be made. It is assumed that in normal use, the case b) cannot occur subsequently to a case c). If this does occur, nevertheless, the starting value at a pressure drop will be used as the difference in height level h.sub.pat.

Embodiments

[0058] The method according to the invention for determining the difference in height level h.sub.pat between patient (10) and fluid feed pump (5) is as follows:

[0059] The initial situation is the provision of the fluid feed pump (5) comprising a reservoir (1) arranged thereabove, wherein the fluidic connection paths in the devices according to the application are provided, are, however, still unfilled. The pump device was turned on and is ready to work, the self test is completed.

[0060] In a first step, the fluid feed pump (5) feeds, through the through-going fluidic connection of the reservoir (1), the fluid and stops feeding, as soon as the pressure sensor (6) detects a change in pressure, which in this situation is caused by the fed water column. Thereby, by the measurement value of the pressure sensor, under the condition of an empty tube (3, 7), the situation can be detected that the fluid column extends from the reservoir (1) to the fluid feed pump (5) and the rest is filled with air.

[0061] The mentioned stop of feeding consists—if a pressure sensor (11) is attached hydraulically shortly before or above the transport roller wheel (4)—in that the value measured at this optional pressure sensor (11) is maintained for further processing, which not necessarily means a standstill of the transport roller wheel (4). If no other pressure sensor (6) than the one shown in FIGS. 1 to 3 is available, then the transport roller wheel (4) is turned backward. From a measurement of the motor current required for feeding from the tube section (3) to the reservoir (1) (also for the backward feeding), the generated torque is derived. The torque is calculated with the diameter of the transport roller wheel as a force and is calculated, together with the previously known effective area of the tube cross-section, as a pressure value (force/surface area), from which the height between the fluid level in the reservoir (1) and the hydraulically effective height of the transport roller wheel (4) is obtained.

[0062] Between the hydraulically effective height at the transport roller wheel (4) toward the reservoir (1) and the hydraulically effective height at the transport roller wheel (4) toward the patient (10), there is, if applicable, a difference that has to be determined beforehand.

[0063] After the pressure P.sub.wat or the height value between the fluid level in the reservoir (1) and the fluid feed pump (5) has been determined, the tube and instrument filling process is continued, i.e., the pump (5) continues to feed fluid in the direction of the patient (10). Feeding continues until the tube section (7) is completely filled. When the fluid exits from the open end of the tube section (7) or the instrument (9), which is detected by the cease of the pressure increase described above (embodiment) or by that the fed volume is larger than the volume of the tube of the tube section (7) between feeding segment and outlet end (alternative embodiment), the filling phase/feeding is terminated. This means in reality that the pump feeds from this point of time on with constant volume flow, whereupon a constant pressure value at the pressure sensor (6) is obtained, and the pressure value is evaluated in relation to the fed volume. In an alternative embodiment, the fed volume is evaluated, and the fed volume is determined from the turns of the transport roller wheel (4) and the previously known feeding volume per turn. The fluid feed pump (5) is stopped, and the pressure value of the pressure sensor (6) is evaluated. When the pressure value is positive, this pressure value is used to determine the height level between the transport roller wheel (4) and the patient (10), and thereby it is assumed that in this case, the pump (5) is below the height level of the patient (10).

[0064] When the pressure value is negative, the measured pressure value is used as P.sub.hyd, or therefrom the difference in height level h.sub.pat is determined, and thereby it is assumed that in this case, the pump (5) is above the height level of the patient (10).

[0065] When the pressure value is 0 (zero), it is assumed that in this case, the pressure sensor (6) cannot measure negative values, and that the pump (5) is above the height level of the patient (10). When this is the case, the transport roller wheel (4) is turned backward, and the motor current required for feeding from the tube section (7) to the reservoir (1) (i.e., for backward feeding) is measured, and therefrom the generated torque is derived. The torque is calculated with the diameter of the transport roller wheel as a force and is calculated together with the previously known effective area of the tube cross-section as a pressure value (force/area), which yields the height level between the transport roller wheel (4) and the height level of the patient (10).

[0066] When the pressure value, after a predetermined time, does not become a stationary value, it is assumed that in this case, the outlet end is placed in the cavity. The predetermined time follows from the tube filling time given by the feeding rate and the cross-sectional area of the tube plus optionally a small addition for rinsing-out of air bubbles. In the case that the outlet end is already in the cavity, then according to the invention, the pressure increase is to be evaluated, in order to determine the patient's height level h.sub.pat. The evaluation consists in detecting the course as exemplarily shown in FIG. 4, and using the value at the point of time to as the hydrostatic pressure P.sub.wat or, derived therefrom, to determine the difference in height level h.sub.pat between pump (5) and patient (10). It is necessary, herein, that a constant volume flow of the fluid is generated.

[0067] According to the invention is also provided a test, as to whether there is an open end of the tube section (7) or instrument (9), since a connector with an outlet valve (8) is provided that may be closed, and clamps may be attached at the tube. This method considers the pressure values together with the fed fluid volume. When a volume flow is fed, and the pressure moves toward a constant value at the pressure sensor (6), it is assumed that in this case, the tube section (7) is open to ambient pressure. When feeding is stopped, the pressure will decrease, and the measurement value at the pressure sensor (6) decreases. When these measurement values occur in the flow and pressure course, it is assumed that in this case, the end of the tube section (7) is open to ambient pressure.

[0068] When the flow values are zero, and the pressure remains stable or decreases slightly only, it is assumed that in this case, the end of the tube section (7) is closed to ambient pressure. In the case that the tube filling process is just terminated, it is assumed that in this case, the outlet valve at the connector (8) is closed, or a clamp clamps the tube section (7) off. In this case, in the further course of the use of the pump (5), a user will verify the tube filling process, which means that the outlet valve of the connector (8) is shortly opened and closed, and some fluid will escape. The pressure sensor (6) detects the pressure drop by opening the outlet valve at the connector (8), whereupon, as intended, the feeding of the fluid feed pump (5) will start, in order to maintain the preset pressure. Since the fluid feed pump (5) has detected the situation, the pressure value of the hydrostatic pressure, as already described, is determined by the pressure sensor (6) or the backward feeding, and so to speak retrospectively, the pressure value at the start of feeding or with still closed valve (8) is taken as the value P.sub.wat, or the patient's height level h.sub.pat is determined therefrom.

LIST OF REFERENCES

[0069] Outlet end refers to the transition of the fluid line behind the transport roller wheel (4) to ambient pressure or to the cavity. This may be the end of the tube section (7) or the end of the outlet valve (8) or the end of the instrument (9), depending on where ambient pressure acts, when the method according to the invention is applied. [0070] h.sub.pat—patient's height level=hydraulically effective height level between the transport roller wheel (4) and the patient (10) [0071] P—pressure [0072] P.sub.m—draw-in pressure [0073] P.sub.cav—cavity pressure [0074] P.sub.drv—feed pressure [0075] P.sub.hyd—hydrostatic pressure of the fluid in the tube [0076] (1) reservoir of the fluid. [0077] (2) spikes forming a connection between reservoir and tube (3). Usually, clamping devices may be provided here for a container exchange. [0078] (3) tube section of the tube set between reservoir (1) or spikes (2) and transport roller wheel (4), also fluid line. [0079] (4) transport roller wheel. [0080] (5) fluid feed pump or pumping device or pump. [0081] (6) pressure sensor—bidirectional design (measures also negative pressures in relation to ambient pressure) or unidirectional design (measures only pressure values above ambient pressure). [0082] (7) tube section between fluid feed pump (5) and connection to a connector (8) or instrument (9), also fluid line. [0083] (8) connector with outlet valve, optionally provided. [0084] (9) instrument, which is introduced into the cavity to be expanded and from the end of which the fed fluid exits into the cavity. Frequently, a combination of sleeve (=trocar) and endoscope or shaver. [0085] (10) patient=region of surgery=surgery area=cavity=body cavity. [0086] (11) optional pressure sensor, hydraulically shortly above the transport roller wheel (4). [0087] (12) current sensor at the motor that moves the transport roller wheel (4) of the fluid feed pump (5) (not shown in the Figures).

DESCRIPTION OF FIGURES

[0088] FIG. 1 shows a medical fluid pump and a body cavity in which the body cavity is located higher than the fluid pump. The difference in height is calculated using data from a single pressure sensor in the fluid line between the fluid pump and the body cavity.

[0089] FIG. 2 shows a medical fluid pump and a body cavity in which the body cavity is located higher than the fluid pump. The difference in height is calculated using data from two pressure sensors.

[0090] FIG. 3 shows a medical fluid pump and a body cavity in which the body cavity is located lower than the fluid pump. The difference in height is calculated using data from a single pressure sensor in the fluid line between the fluid pump and the body cavity.

[0091] FIG. 4 shows the relationship between liquid feed with a pump and the pressure reading in a situation in which the outlet of the fluid line is located in a closed cavity of the patient ( discussed on page 16 of the specification)