Coagulation device comprising an energy control

Abstract

A device (10) for tissue coagulation, in particular for fusion, encompasses an electric source (18), which is connected or which can be connected to electrodes (12, 13) for influencing biological tissue (11) with current. A control unit (22) controls the source (18) during phases I and II of the tissue fusion. These phases I and II correspond to operating phases I, II and III of the device (10). During operating phase I, a monitoring unit (23) determines the energy E.sub.1, which is applied into the tissue (11). In the subsequent operating phases II and III, the control unit (22) controls the source (18) by means of the determined energy E.sub.1. Such a device turns out to be particularly reliable and to be robust in use.

Claims

1. A device (10) for tissue coagulation, the device comprising: an electric source (18), configured to be connected to electrodes (12, 13) for influencing biological tissue (11) with current, a monitoring unit (23), which is connected to the electric source (18), configured to determine one or both of a current (I.sub.ACT) output by the electric source (18) and a voltage (U.sub.ACT) output by the electric source (18), a control unit (22), which includes the monitoring unit (23) and which is connected to the electric source (18) in a controlling manner, the control unit (22) configured to: determine an energy value (E1) which corresponds to a total amount of energy the electric source (18) outputs to the electrodes (12, 13) during a first operating phase (I), and control the electric source (18) as a function of the energy value (E1), which is determined in the first operating phase (I), in a subsequent second operating phase (II), wherein at least one of a minimum and a maximum duration of the second operating phase (II) is defined according to the energy value (E1) from the first operating phase (I).

2. The device according to claim 1, wherein the control unit (22) is interconnected with the electric source (18) in the first operating phase (I) as a current regulating circuit.

3. The device according to claim 1 wherein at an onset of the first operating phase (I), the control unit (22) is configured to define a chronologically increasing current (i1a).

4. The device according to claim 1 wherein during at least a section (Ib) of the first operating phase (I), the control unit (22) is configured to define a constant current (i1b).

5. The device according to claim 1 wherein the control unit (22) comprises a module (26) configured to determine a conclusion of the first operating phase (I) using at least one of: a relationship between voltage and current at the electric source (18) increases beyond a threshold value (R.sub.Gmax), the relationship between voltage and current at the electric source (18) passes through a minimum (M), an increased speed of change in the relationship between voltage and current at the electric source (18) exceeds a threshold value, the voltage (U.sub.ACT) at the electric source (18) exceeds a threshold value, the current (I.sub.ACT) falls below a threshold value.

6. The device according to claim 1 wherein at an onset of the second operating phase (II), the control unit (22) is equipped to adjust at least one variable of: current (I.sub.ACT) from the electric source (18), voltage (U.sub.ACT) at the electric source (18), output power (P.sub.ACT) of the electric source (18) to a same value the variable had at a conclusion of the first operating phase (I).

7. The device according to claim 1 wherein in the second operating phase (II), the control unit (22) is configured to define a course of time for changing of a relationship between the voltage (U.sub.ACT) at the electric source (18) and the current (I.sub.ACT) supplied by said source.

8. The device according to claim 7, wherein the course of time encompasses a constant impedance increase (A).

9. The device according to claim 1 wherein the control unit (22) is configured to define a chronological length (t2) of the second operating phase (II).

10. The device according to claim 1 wherein the control unit (22) is configured to define a chronological length (t2) of the second operating phase (II) as a function of the energy value (E1), which is determined in the first operating phase (I).

11. The device according to claim 1 wherein directly following the second operating phase (II), the control unit (22) is configured to merge into a third operating phase (III).

12. The device according to claim 11, wherein in the third operating phase (III), the control unit (22) is configured to define and adjust a constant voltage (U3).

13. The device according to claim 11, wherein in the third operating phase (III), the control unit (22) is configured to define a voltage (U3) of the electric source (18) to a value determined by the monitoring unit (23) at a conclusion of the second operating phase (II).

14. The device according to claim 11, wherein the control unit (22) is configured to conclude the third operating phase (III), if: a minimum treatment time (t.sub.min) and a given total energy (E.sub.tot) have been reached or a maximum treatment time (t.sub.max) has elapsed or a maximum energy (E.sub.max) has been applied.

15. The device according to claim 11, wherein the control unit (22) is equipped to monitor a power output by the electric source (18) in the operating phase (II), so as to extend a time period (t2) for the second or third operating phase (II, III), provided that the power has left a performance window, which is defined between a maximum power (P.sub.max) and a minimum power (P.sub.min).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the device according to the invention in schematic illustration.

(2) FIG. 2 shows a control unit for the device according to FIG. 1, in a sectional schematized block diagram and

(3) FIG. 3 shows time diagrams for explaining the function of the control unit.

DETAILED DESCRIPTION

(4) FIG. 1 illustrates a device 10 for coagulating biological tissue 11, which can be a hollow vessel or also any other biological tissue, for example. In the following example, a blood vessel is illustrated as tissue 11, which is to be closed by means of coagulation, that is, a fusion of the walls of the vessel, which are located opposite one another, is to be carried out. Two electrodes 12, 13, which can seize the tissue 11 between one another and which can also stress it mechanically, for example by means of compression, serve this purpose. The mechanical structure of the corresponding instrument is not illustrated in detail in FIG. 1. For example, the electrodes 12, 13 can be the branches of a bipolar fusion instrument.

(5) The electrodes 12, 13 are connected to a feeding device 15 via a line 14. For this purpose, the line 14 encompasses two leads 16, 17, for example, to which the device 15 supplies or can supply high-frequency current.

(6) For this purpose, the device 15 encompasses a source 18, for example in the form of a controllable HF generator 19. The latter can be supplied with operating voltage via a power supply 20 and a power connector 21 via a mains power supply.

(7) The HF generator 19 and/or the power supply 20 are embodied so as to be controllable. At their corresponding controls inputs, a control unit 22, which controls or regulates in particular the output of electric power through the HF generator 19, is connected, as is illustrated by means of arrows. For this purpose, the control unit 22 includes a monitoring unit 23, which determines the electric variables of the electric energy, which is supplied to the electrodes 12, 13. In particular, the monitoring unit 23 is equipped to determine and integrate the electric power supplied to the electrodes 12, 13 at least temporarily, so as to establish the energy, which is supplied during a time interval. The monitoring unit 23 can encompass a voltage block 24 for monitoring the voltage applied at the clamps 12, 13. In addition, the monitoring unit 23 can encompass a current block 25 for establishing the size of the current, which is supplied to the electrodes 12, 13. The control unit 22 can furthermore encompass a module 26 for defining the conclusion of a first operating phase I, wherein the module receives at least one output signal from the voltage block 24 or from the current block 25 or a signal derived from the output signals thereof for recognizing the end of the operating phase.

(8) In FIG. 2, the control unit 22 is illustrated in a schematically simplified manner and only in excerpts. The current block 25 determines the current I.sub.ACT, which flows through the tissue 11. The actual voltage U.sub.ACT, which is applied to the tissue 11, is determined by means of the voltage block 24. The power P.sub.ACT, which is actually supplied to the tissue 11, is calculated from both variables, at least temporarily. The power P.sub.ACT can be the determined active power or also the apparent power, which is supplied to the electrodes 12, 13. A corresponding block serves the purpose of calculating the power P.sub.ACT or for determining it otherwise.

(9) The control unit 22 can furthermore encompass a current default block 28, which provides a current I.sub.REF as a function of time and/or situation. Likewise, provision can be made for a voltage default block 29, so as to provide a desired voltage U.sub.REF. The current default block 28 and the voltage default block 29 can be controlled by an impedance block 30, which defines a desired relationship between the voltage U.sub.REF and the current I.sub.REF as a function of time or situation, for example so as to define a desired tissue resistance R.sub.G or a desired chronological course thereof.

(10) The reference-actual deviations for the current I.sub.ACT and the voltage U.sub.ACT are in each case formed in corresponding differential forming blocks 31, 32 and are supplied to a processing module 33. The latter controls the generator 19.

(11) The processing module 33 furthermore includes the module 26 for recognizing various operating phases. This module 26 can obtain at least the actual current I.sub.ACT and/or the actual voltage U.sub.ACT or a value, which is derived from these variables, as input variable (via non-illustrated signal paths).

(12) An energy block 34 for determining the energy supplied to the tissue 11 is connected to the block 27 for establishing the power. Said energy block integrates the measured power P.sub.ACT for a period of time, which is provided by the processing module 33, and supplies the integral to the processing block 33.

(13) It is pointed out that the blocks 27 to 32 as well as 34 can also be part of the processing module 33.

(14) The further design of the device 15 and in particular of its control unit 22 follows from the following description of the time behavior thereof:

(15) It is assumed that living, non-denaturized tissue 11, is initially seized between the electrodes 12, 13. At its activation input 35, the device 15 now receives the signal for coagulation and, if applicable, for fusion of the biological tissue 11. This corresponds to the starting point or activation onset , respectively, which is noted in FIG. 3. Operating phase I initially starts with a partial phase Ia. In the latter, the current I.sub.ACT is brought to a desired current value of 4 A, for example, in a controlled manner. The current can thereby be brought from an initial value, such as 1 A, for example, to the reference value of 4 A, for example, within a period of time t.sub.1a. This can take place in a linear ramp: the time for this can be between 200 ms and 2 s. Preferably, the effective value of the current is used as measuring variable. The tissue resistance R.sub.G decreases from an initial value to a minimum value of between 2 Ohm and 40 Ohm, for example, during this phase or also completely or partially in a later operating phase Ib. Due to the increase of the current, the voltage U.sub.ACT increases during the time period t.sub.1a. During this time, the current I.sub.ACT is preferably increased in the form of a ramp. For example, the peak voltage between the electrodes 12, 13 can be measured as measuring value for the voltage U.sub.ACT. In operating phase I, the current I.sub.ACT is then held constant at the value i.sub.1b during a further partial phase Ib. The control unit 22 thereby operates as current regulating circuit for keeping the value i.sub.1b constant.

(16) During the first partial phase Ia or during the second partial phase Ib, the tissue resistance R.sub.G passes through a minimum, so as to then increase again. If the tissue resistance minimum is already reached in the first partial phase Ia, the partial phase Ib can be skipped and a direct transition into operating phase II can be made. The power limit of the generator 19 might possibly be reached thereby, so that the current regulating circuit is no longer able to bring the current I.sub.ACT into conformity with the desired current I.sub.REF. Towards the end of operating phase I, the current thus decreases. Depending on the embodiment, this decrease of the current i.sub.1b or also the current differential value (I.sub.REF−I.sub.ACT), which is formed by the differential forming block 31, can be used as indicator for the conclusion of operating phase I. It is also possible for the control unit 22 to establish the tissue impedance R.sub.G as quotient from U.sub.ACT and I.sub.ACT and to determine the conclusion of operating phase I, if the tissue resistance exceeds a given threshold. In the alternative, the increase speed for the tissue resistance R.sub.G can also be monitored. According to this, the control unit 22 can use the following criteria to recognize operating phase I, either cumulatively or as alternatives: detecting the pass-through of the minimum of the tissue impedance or of the tissue resistance dR/dt=0) falling below a threshold value of the current I.sub.ACT, for example 0.5*i.sub.1b exceeding a threshold value of the tissue impedance, for example 80 Ohm exceeding a threshold value of the increase speed of the tissue impedance (dR/dt).

(17) During the entire operating phase I, the energy block 34 integrates the power established by the block 27 and supplies the established value of the energy E.sub.1 to the processing module 33 at the conclusion of operating phase I. The onset and the conclusion of operating phase I are marked by means of the points in time and t.sub.1. The point in time t.sub.1 is determined by the processing module 33 according to one of the above-mentioned criteria.

(18) Operating phase II starts with the conclusion of operating phase I. Operating phase II preferably starts with the same current I.sub.ACT, with which operating phase I concluded. In addition, it preferably begins with the same voltage U.sub.ACT, with which the first operating phase I concluded. Operating criteria are now defined for operating phase II by means of the applied energy E.sub.1, which was established in operating phase I. In operating phase II, the generator 19 is preferably operated in an impedance-regulated manner, that is, the control unit 22 forms a regulator for the tissue impedance. A desired chronological impedance increase A is defined for the tissue impedance. In FIG. 3, the impedance increase A is illustrated as R.sub.Gref as desired dashed line over the course of time. The actual impedance increase R.sub.Gact can deviate slightly from this. This depends on the control quality of the impedance regulator, which is now formed by the control unit 22. At the same time, the current I.sub.ACT decreases during operating phase II, that is, during the period of time t.sub.2, while the voltage U.sub.ACT increases. The voltage U.sub.act has an upper limit, e.g. 150V (peak value), so that it is avoided that sparks appear and that a cutting effect would thus be caused.

(19) The impedance increase A can be between 50 and 200, preferably 100 Ohm per second. The specific slow increase of the impedance causes a stabilization of the evaporation of the tissue fluid.

(20) Operating phase II is concluded, when the period t.sub.2 has elapsed. The period t.sub.2 can be established from the energy E.sub.1 as follows:
t.sub.2=⅔(t.sub.max−t.sub.1).

(21) The time t.sub.max is thereby the maximum treatment period. The maximum treatment period t.sub.max can be calculated from the minimum treatment period, in that a constant defined summand is added, for example:
t.sub.max=t.sub.min+1.8 s

(22) The minimum treatment period t.sub.min can be determined, for example, from the following relationship from the energy E.sub.1:
t.sub.min=min {5.4 s;(−38.25 μs*E.sub.1.sup.2/J.sup.2+18 ms*E.sub.1/J+270 ms)}.

(23) According to this, t.sub.min is a defined value of 5.4 s, for example, or which results from calculating the round bracket, depending on which value is less.

(24) With the conclusion of operating phase II, operating phase III begins. In the latter, the voltage U.sub.ACT is constantly regulated to the value U.sub.3 for a period of time t.sub.3. The control unit 22 operates as a voltage regulator circuit herein.

(25) During operating phases II and III, which correspond to phase II of the tissue coagulation, the power is integrated further. When this value reaches the total maximum value E.sub.tot, the treatment is concluded. The total maximum value E.sub.tot can be established according to various empirically obtained formulas as a function of the energy E.sub.1, for example as follows:
E.sub.tot=45J+2.75*E.sub.1.

(26) In the alternative, the reaching of the maximum period t.sub.3 of operating phase III can be recognized. This period t.sub.3 can be calculated, for example according to:
t.sub.3=⅓*(t.sub.max−t.sub.1).

(27) To avoid improper treatments caused by unforeseen changes of the treatment parameters, for example by accidentally opening the fusion clamps, it can additionally be monitored, whether the actual power leaves a performance window from P.sub.min and P.sub.max within a monitoring time interval, for example during operating phase II and/or III.

(28) A device 10 for tissue coagulation, in particular fusion, encompasses an electric source 18, which is connected or can be connected to electrodes 12, 13 for influencing biological tissue 11 with current. A control unit 22 controls the source 18 during phases I and II of the tissue fusion. These phases I and II correspond to operating phases I, II and III of the device 10. During operating phase I, a monitoring device 23 determines the energy E.sub.1, which is applied into the tissue 11. The control unit 22 controls the source 18 in the subsequent operating phases II and III by means of the determined energy E.sub.1. Such a device turns out to be particularly reliable and to be robust in use.

LIST OF REFERENCE NUMERALS

(29) 10 device 11 biological tissue 12, 13 electrodes 14 line 15 device 16, 17 leads 18 source 19 HF generator 20 power supply 21 power connector 22 control unit 23 monitoring unit 24 voltage block 25 current block 26 module for recognizing operating phases U.sub.ACT voltage (e.g. peak value) I.sub.ACT current (e.g. effective value) P.sub.ACT power 27 block for establishing power 28 current default block I.sub.ACT desired current 29 voltage default block U.sub.REF desired voltage 30 impedance block R.sub.G tissue resistance 31, 32 differential forming blocks 33 processing module 34 energy block 35 activation input activation onset I first operating phase Ia partial phase t.sub.1a period of the first partial phase Ib partial phase i.sub.1a value of the current I.sub.ACT in the partial phase Ia i.sub.1b value of the current I.sub.ACT in the partial phase Ib t.sub.1 period of operating phase I E.sub.1 energy input into the tissue 11 in phase I A impedance increase R.sub.Gref desired impedance course R.sub.Gact actual impedance course t.sub.2 period of operating phase II t.sub.max maximum period of treatment t.sub.min minimum period of treatment E.sub.tot total maximum value of the energy t.sub.3 period of operating phase III t.sub.tot total period of treatment R.sub.Gmax threshold value for tissue resistance in operating phase I M minimum of the tissue resistance in operating phase I U.sub.3 voltage in operating phase III P.sub.max, P.sub.min define performance windows for the power P of the source 18 in operating phases II and/or III