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The invention relates to a device for sterilizing human females by
transuterine tube coagulation, comprising a high frequency generator and a
probe which is connected thereto and which comprises an active electrode.
It is possible to sterilize human females, in the so-called transuterine
tube coagulation method, by sealing the lumen of the tubes leading to the
uterus by electric coagulation of the tissue. According to a known method,
(see, for example, an article by H. J. Lindemann in "Geburtsh. und
Frauenheilk.", No. 33 (1973) pages 709-715, published by Georg Thieme
Verlag, Stuttgart), a coagulation probe is moved to the tube under visual
control by means of an hysteroscope. This method is substantially less
disturbing to the patient than an operation through the abdominal wall,
but it still requires narcosis or a local anaesthetic.
The invention has for its object to provide a device for transuterine tube
coagulation whereby the sterilization can be very quickly and accurately
performed without utilizing a hysteroscope and hence without narcosis. To
this end, the device according to the invention is characterized in that
the probe is formed by a flexible catheter comprising on one end a metal
portion which forms the active electrode and which is electrically
connected to a connection which is provided near the other end of the
catheter, the device furthermore comprising indicating means for providing
information as regards the variation of the current and the voltage
delivered by the generator.
The catheter can be positioned under X-ray control, after which the metal
electrode closes the opening of one of the tubes leading to the uterus
like a cork closes a bottle. This can be checked by injecting an X-ray
contrast liquid via the catheter. When the electrode has been properly
positioned, only the tube gives X-ray contrast and the uterus itself does
not. The current and voltage values give an indication which enable the
coagulation process to be followed and terminated at the most suitable
instant without visual checking. The indicating means preferably comprise
a first lamp which lights up when the voltage on the electrode increases
beyond a given value, and a second lamp which extinguishes when the
current applied to the electrode decreases below a given value. In order
to accurately follow the coagulation process, it may furthermore be
important to monitor the variation of the resistance of the tissue and the
power delivered to the tissue. These quantities can be calculated from the
measured current and voltage by means of suitable calculating members.
In order to check the circuit formed by the generator, the electrode and
the tissue for an open circuit and possibly dangerous defects after the
positioning of the electrode, just prior to the beginning of the
treatment, there is preferably provided a switch whereby the catheter
connection can be connected to the generator via a circuit which limits
the current intensity supplied by the generator to a value which is
substantially lower than the current intensity required for tissue
coagulation, while a measuring instrument is provided for measuring at the
same time the voltage on the connection.
The invention will be described in detail hereinafter with reference to the
drawing.
FIG. 1 diagrammatically illustrates the principle of a device according to
the invention,
FIG. 2 shows the variation of the current and the voltage during
sterilization.
FIG. 3 shows a block diagram of the device according to the invention, and
FIG. 4 is a front view of a control unit for this device.
FIG. 1 diagrammatically shows a uterus 1 and tubes 3 opening therein. A
thin flexible catheter 5 has been introduced to the uterus. An end portion
of this catheter has been bent to be approximately S-shaped, with result
that the end of the catheter automatically searches the opening of one of
the fallopian tubes 3. This end portion is partly made of metal in order
to form an active electrode 7 which is connected, via a conductor (not
shown) extending in the wall of the catheter 5 to a metal connection
portion 9 near the other end of the catheter, which in its turn is
connected, via a conductor 11, to the electronic section 13 of the device
which will be described in detail hereinafter with reference to FIG. 3.
The internal cavity of the catheter is connected to a known pumping device
15 for injecting X-ray contrast liquid. When the catheter 5, inserted
under X-ray control, is slid slightly further than the position shown, the
electrode 7 closes off the tube 3 like a cork closes a bottle. When
contrast liquid is then injected by means of the pumping device 15, only
the tube 3 will be clearly visible in the X-ray image. When closure by the
electrode 7 is complete, contrast liquid will also penetrate into the
uterus 1; this can be clearly observed in the X-ray image.
After the X-ray check has revealed that the electrode 7 occupies the
correct position, the electronic section 13 is activated. This section
delivers a series of current surges of high frequency, for example 2 MHz
as is commonly done for tissue coagulation (see, for example, U.S. Pat.
No. 3,675,655. Normal tissue contains a larger quantity of moisture and
hence has a low specific resistance. During and after the coagulation
process by means of high frequency energy, this moisture evaporates and
the tissue is dessicated. If the application of high frequency energy is
continued, the tissue carbonizes. During the dessication phase the
specific resistance of the tissue substantially increases; this becomes
manifest in an increase of the voltage and a decrease of the current. This
is shown in FIG. 2, wherein the current I and the voltage V are plotted as
a function of the time. The dessication commences at the instant t.sub.1
and the carbonizing commences approximately at the instant t.sub.2 at
which the treatment is terminated.
The object of transuterine tube coagulation is to damage the tissue of the
tubes 3 such that scar tissue is produced which effectively seals the
opening of the tubes. It has been found that an optimum effect is achieved
if the coagulation is terminated approximately at the indicated instant
t.sub.2,i.e. during or shortly after the end of the desication phase. As
appears from FIG. 2, this instant is characterized by a voltage V.sub.2
and a current I.sub.2. It has been found that proper control of the
process can be achieved by measuring the r.m.s. values of current and
voltage, and particularly by indicating the reaching of the values I.sub.2
and V.sub.2. To this end, the electronic section 13 can be constructed as
shown by FIG. 3 in the form of a block diagram.
One output 19 of a known high frequency generator 17 (see, for example,
said U.S. Pat. No. 3,675,655) is earthed via a resistor 21, while the
other output 23 is connected to the catheter connection 9 via a control
unit 25 and the conductor 11.
The control unit 25 comprises a switch 27 which, in the position shown,
connects the generator output 23 to the connection 9 via a voltage divider
formed by a capacitor 29 and a resistor 35. This voltage divider is chosed
such that the generator current remains limited to a value which lies
substantially below the current required for tissue coagulation. The
voltage on the connection 9 (which is also substantially below the
generator voltage) is then a measure of the resistance of the series
circuit formed by the construction 9, the conductor in the catheter 5, the
active electrode 7, the tissue of the patient and an earthed neutral
electrode (not shown). If this series circuit does not include poor
contacts, its resistance amounts to approximately 150 .OMEGA.. A poor
contact in the circuit can be caused, for example, by the neutral
electrode inadequately contacting the skin of the patient. A poor contact
becomes manifest in a substantially high resistance and may be hazardous
to the patient.
The voltage on the connection 9 is measured by a rectifier bridge 31 with a
measuring instrument 33. The bridge 31 is connected, via the said resistor
35, to the capacitor 29. When the desired measurement reveals that
everything is in order, the switch 27 can be switched over, after which
the output 23 of the generator 19 is connected to the connection 9 via an
incandescent lamp 39. In comparison with the said series circuit, the
incandescent lamp 39 has a low resistance, so that the full generator
current I.sub.0 (see FIG. 2) can flow. The incandescent lamp 39
extinguishes substantially completely when the current decreases
substantially, i.e. approximately at the instant t.sub.2.
The connection 9 also has connected thereto, via a voltage divider formed
by two resistors 41, 43, a gas discharge lamp 45. The gas discharge lamp
45 lights up when the voltage on the connection 9 reaches a given value,
for example V.sub.2. The output voltage at which the gas discharge lamp
lights up depends on the value of the resistor 41 and can be varied, if
desired, by making this resistor variable. Due to these provisions, the
reaching of the instant t.sub.2 can be readily observed by the physician
on the basis of the extinguishing of the lamp (39) and the approximately
simultaneously lighting up of the lamp 45. The control unit 25 is
preferably constructed as a case which can be easily held in the hand and
which comprises a front panel whereon the lamps (39) and 45, the meter 33,
a control knob 47 for the switch 27 and a control knob 49 for an on/off
switch (not shown in FIG. 3) are provided (see FIG. 4). A first cable 51
connects the control unit 25 to the generator 17; a second cable 53 leads
to the catheter connection 9, and a third cable 54 leads to the neutral
electrode.
Besides by means of the control unit 25, which keeps the physician directly
informed as regards the progress of the coagulation process, current and
voltage measurements can also be effected at the area of the generator 17.
The results of these measurements can be used for obtaining further
information as regards the progress of the process or for controlling the
generator. To this end, the output 23 of the generator 17, carrying the
voltage V, is connected, via a conductor 55, to a multiplier 57 and a
divider 59 which are known per se and which are not elaborated herein. The
output 19, carrying a voltage proportional to the current I due to the
resistor 21, is also connected, via a conductor 61, to the multiplier 57
and the divider 59.
The multiplier 57 calculates the product V.I. which corresponds to the
r.m.s. value of the power P delivered by the generator 17. The divider 59
calculates the quotient V/I which corresponds to the load resistance R of
the generator 17 which is mainly determined by the specific resistance of
the treated tissue and which thus provides direct information as regards
the progress of the coagulation process. Voltages which are proportional
to P and R are applied, via conductors 63 and 65, respectively, to a known
control unit 67 which controls the generator 17. If desired, the values of
P and R can also be displayed in known manner (not shown).
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