Note: Descriptions are shown in the official language in which they were submitted.
The invention relates to a triyger for therapeutic
acoustic shock waves, for instance for comminuting kidney
stones.
An instrument Eor the contactless comminution of
concretions in bodies of living tissue ~y means of shock
waves is known (note U.S. Patent No. 3,942,531). In this
instrument, elec-tric discharges along a submerged spark gap
generate acoustic shock waves in a focusing chamber, outside
the body, the shock waves being focused on the concretion
and comminuting it. These shock waves pass through the
body tissue without damaging it. However, extrasystoles may
be triggered in the stimulative phase of the heartbeat.
Accordingly, the heart rhythm can be disturbed in patients
with circulatory problems. In that case adequate circulation
of the blood no longer will be ensured. Moreover, care must
be taken when selecting the trigger time that the coordi-
nates of the target, for instance the kidney - which are
periodically changing due to breathing - shall be as constant
as possible at the time of the shock wave triggering in order
to achieve a high impact probability.
An object of the present invention is to provide
an instrument correlating the trigger time of the shock wave
for example to the heart action in such a manner that the
heart rhythm cannot be disturbed. The present invention
also relates to a method of comminuting concrements in the
body of a human being by shock waves.
This problem is solved by the invention by means
of an instrument triggering the shock wave by the QRS peak
of the EKG, or by triggering with a selective time-delay
thereafter.
One of the advantages of the present invention is
that shock waves can be appli~ed to patients with impaired
blood circulation and that this group of patients also can
be spared surgical intervention. The physician is relieved,
9;~
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by the automatic time correlation with the heartbeat
and/or further body functions, fxom the task of matching
the shock wave application to the body rythms. This
permits avoidance of erroneous steps.
According to the present invention there is
provided a trigger instrument for triggering shock waves
for the con-tact-free communication of concretions,
characterised by a plurality of channels for measuring
various periodic body functions, each having:
a) a measured value pick-up for one of the
body functions,
b) a circuit which obtains a trigger pulse
from an extreme value of a measuring signal supplied by
the measured value pick-up,
c~ an adjustable delay device which emits the
trigger pulse with a timing delay,
and by an AND-gate to which the outputs of a]l measuring
channels are connected and which, upon simultaneous
arri~al of trigger pulses from all channels, delivers
20 to the shock wave source a signal pulse via a manually
actuated release switch.
Preferably, there are two signal channels each
for a body function.
Preferably, the AND-gate has two inputs, which
25 corelates two input signals, coming from said two
signal channels.
Preferably, the AND-gate has an output
which is zero or logic low if there is no pulse or only
one pulse at the inputs and said AND-gate has an output
30 which is a pulse or logic high if there are pulses
at both inputs at the same moment, so that an output
pulse is only available at said moment, when the time
delay after one QRS peak of an EKG probe forming said
test-value pick-up corresponds with one phase of exhaled
state at a time the heartbeat is not vulnerable and
3~Z~7~
the motion of the body, induced by breathing, is zero.
The measured value pick-up may be an EKG
probe, the extreme value belng the QRS peak of the
EKG, ot is may be a respirometer, a phase of the
exhaled state being the extreme value.
Preferably, the trigger instrument may include
means whereby the circuit extracts a trigger pulse
from every second, third, etc. extreme value~
In a preferred aspect a first one of said
channels may include a measured value pick up for an
EKG signal, and a second one of the channels may include
a measured value pick up for respiration, a coincidence
circuit being provided for responding to an extreme
value in the EKG signal as pickedup through the first
channel and to an exhaling state as picked up by
the pick up of said second channel~ to obtain the trigger
signal in response to a coincidence.
Preferably, a danger free trigger time
for applying acoustic shock waves is at a predetermined
time after said extreme value.
Preferably, the adjustable time-delay and
the circuit receiving a pulse and producing another
pulse at a predetermined time, are combined in a pulse
generator, and the switch is open most of the time and
interrupts the signal channel, a signal pulse being
transmitted to the shock wave upon closure of said
switch.
With the present trigger instrument the method
of comminuting concrements in the body of a human
by means of therapeutic acoustic shock waves comprises
the steps of:
picking up a periodic body function and
extracting from a picked up value a particular, perio-
dically recurring indication;
adjustably delaying a representation of said
indication;
providing for triggering a shock wave in
direct xesponse to said delayed representation and in
dependence upon a manual release when made; and
providing said manual release to obtain said
trigge.ring.
According to one aspect of the method there
is provided a method of generating shock waves for
comminuting concrements in the body of a human being,
comprising the steps of:
picking up a plurality of periodic body
functions;
extracting from each representation as resulting
from said picking up particular recurring values;
adjustably delaying each said pick-up value;
combining in a logic coincidence function the
delayed particular picked~up values for establishing
manually releasing said trigger pulse for
triggering the generation of a shock wave for initiating
said comminuting.
The invention will be better understood b~ the
description that follows of a preferred embodiment thereof,
made with reference to the appended drawings wherein:
Figure 1 shows the EKG voltages as a function of
time for normal heartbeat, ar~d
Figure 2 is a block diagram of an instrument with
further automation by taking into account a second body
function, in this case breathing.
Referring to Figure 1, the terms P,Q, R, S, and T
of the wave function are conventional in medicine. The
steepest rise occurs at the leading edge of the QRS peak
(Figure 1). Point 2 shows a danger-free trigger time for
applying acoustic shock waves. The EKG is recorded in known
manner, and a trigger pulse is obtained in known manner
from the leading edge of QRS peak and fed into a delay system.
This system is adjustable within the range from 0 to lO00
msec and~ depending on the time preselected by the physician
(distance 1-2), delivers a trigger pulse to a spark gap,
which is ignited and then generates an acoustic shock wave.
Referring to Figure 2, two test-signal pick ups,
pick up 3 for the EKG, and pick up 4 (respirometer) for
the breathing motion, feed their test values each to a pulse
generator 5, 6. These generators can be so set that they will
deliver a pulse for a specific phase of the test values,
for instance 10 msec after the occurrence of the QRS peak
or at the time of the breathing pause (phase of the exhalded
state). The outputs of the pulse generators are connected
to the inputs of an A~D gate 7. The output of the gate 7
is supplied through a manual switch 8 to a spark gap
pertaining to a shock wave generator by means of which a
concretion in the body of a patient is comminuted. The
fJ~4
shock wave generator includes additionally an elliptical,
liquid filled coupling device as shown in the above indentified
patent 3,942,531.
Each of the pulse generators 5 and 6 as shown
schematically in Fig. 2 usually comprises a circuit for
extracting an extreme value and a time-delay. The circuit
for extracting the extreme value searches and finds the
extrerne value of the input body function and produces an
electrical pulse at the moment of the extreme value and the
time-delay receives one pluse and produces another pulse at
a predetermines desired time t, i.e. the time between points
1 and 2 in Fig. 1.
A trigger pulse therefore arrives at the spark
gap only when:
a) the physician keeps the switch 8 closed,
b) the breathing motion is nul (phase of the
exhaled state3, and
c) the QRS peak of the EKG has just occurred.
Further body functions may be taken into account
by further parallel signal channels, by the rapidly succeed-
ing triggering of several shock waves, by rapidly succeeding
trigger pulses within one period, and by extracting the
trigger pulse only from every second, third, etc. extreme
value.
With only one channel, a logic combination means 7,
i.e. and AND-Gate is not necessary because thexe is nothing
to correlate with.
The realisation for two body functions comprises
two channels with the elements shown in Fig. 2 and as explained
above, and with the AND-Gate 7 which correlates the two input
signals.
The output of the AND-Gate 7, is zero (logic low)
if there is no pulse or only one pulse at the inputs and its
output is a pulse (logic high) if there are pulses at the both
~2~7~
inputs at the same moment. So one can get an output pulse
only at that moment, when the time delay t after one QRS-peak
corresponds with one phase of exhaled state (= tirne delay
zero after the extreme value of respiration). At this time
the heartbeat is not vulnerable and the motion of the body -
induced by breathing - is zero.
If it is desired or necessary to correlate a third
body function, then a third signal/channel is provided
and the AND-Gate 7 with two inputs is replaced by an AND-Gate
with 3 inputs.
It will be obvious to those skilled in the art
that many modifications may be made within the scope of the
present invention without departing from the spirit thereof,
and the invention includes all such modifications.
