U.S. patent number RE32,091 [Application Number 06/544,892] was granted by the patent office on 1986-03-11 for neuromuscular stimulator.
This patent grant is currently assigned to Medtronic, Inc.. Invention is credited to David J. Stanton.
United States Patent |
RE32,091 |
Stanton |
March 11, 1986 |
**Please see images for:
( Certificate of Correction ) ** |
Neuromuscular stimulator
Abstract
A dual channel neuromuscular stimulator. Pulses developed by a
pulse generator are transmitted alternately on both channels to
involuntarily contract muscles. The stimulator has variable on/off
cycling capability to provide flexibility in meeting the
stimulation needs of patients and has output current adjustments
and other variable parameter settings to achieve optimum
neuromuscular stimulation. To enhance patient comfort, the
stimulation output of the stimulator can be slowly "ramped up" to
its full stimulation power to allow the increase in stimulation to
occur at various rates to accommodate the differing characteristics
of different muscle groups. A jack is provided to permit the
stimulation to be controlled by an external switch operated by a
clinician to coordinate stimulation of various muscle groups with
voluntary muscle contraction by the patient. The jack can also be
connected to a heel operated switch to stimulate muscle groups to
allow certain disabled persons to walk normally. The balanced
biphasic output waveform of the stimulator has a zero net DC
component to minimize the possibility of skin rash developing from
stimulation.
Inventors: |
Stanton; David J. (Anoka,
MN) |
Assignee: |
Medtronic, Inc. (Minneapolis,
MN)
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Family
ID: |
26935939 |
Appl.
No.: |
06/544,892 |
Filed: |
October 24, 1983 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
243558 |
Mar 13, 1981 |
04392496 |
Jul 12, 1983 |
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Current U.S.
Class: |
607/48; 607/64;
607/66; 607/74; 607/70; 607/49; 607/63 |
Current CPC
Class: |
A61N
1/36003 (20130101); A61N 1/36034 (20170801); A61N
1/36 (20130101) |
Current International
Class: |
A61N
1/36 (20060101); A61N 1/08 (20060101); A61N
001/36 () |
Field of
Search: |
;128/419R,421,422,423R,423W |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kamm; William E.
Attorney, Agent or Firm: Duthler; Reed A. Breimayer; Joseph
F. Rooney; John L.
Claims
What is claimed is:
1. A muscle stimulator comprising, in combination:
oscillator means for producing a periodic output signal at a
predetermined repetition rate;
rate control means coupled to said oscillator means for altering
the repetition rate of said oscillator means;
inverter means, coupled to receive the output of said oscillator
means, for producing a periodic output signal having a polarity
opposite to that of the periodic output signal produced by said
oscillator means;
treatment timer means for generating a first logic signal after a
predetermined treatment time interval;
treatment timer control means coupled to said treatment timer means
for establishing the predetermined treatment time of said treatment
timer means;
cycler means for repetitively producing a second logic signal which
remains at a first logic level for a predetermined "on" time
interval and a second logic level for a predetermined "off" time
interval;
first cycler control means completed to said cycler means for
setting the predetermined "on" time interval of said cycler
means;
second cycler control means coupled to said cycler means for
setting the predetermined "off" time interval of said cycler
means;
external switch means;
plug means operatively connected to said external switch means;
accessory jack means constructed and arranged for receiving said
plug means and for providing a third logic signal when said plug
means is inserted in said jack means and said external switch means
is in a particular condition or when said plug is not inserted in
said jack;
momentary contact switch means for producing a fourth logic signal
when said momentary .[.on.]. .Iadd.contact .Iaddend.switch means is
actuated;
first and second ramp generator circuit means connected to receive
said first, second, third and fourth logic signals and for
producing first and second output ramp signals changing from a
first to a second level at first and second predetermined rates,
subsequent to receipt of either of said first, second, third or
fourth logic signals;
first and second ramp generator control means coupled respectively
to said first and second ramp generator circuit means for
independently altering the rate of change of the output ramp
signals of said first and second ramp generator circuit means;
first pulse width circuit means coupled to receive the ramp signal
from said first ramp generator circuit means and to receive the
periodic output signal from said oscillator means and for producing
a fixed amplitude pulse signal having a pulse width increasing at a
rate proportional to the rate of change of the ramp signal from
said first ramp generator circuit means at the predetermined
repetition rate of said oscillator means until the output signal of
said .[.second.]. .Iadd.first .Iaddend.ramp generator circuit means
reaches the second level and the pulse width of the pulse signal
reaches a predetermined pulse width;
second pulse width circuit means coupled to receive the ramp signal
from said second ramp generator circuit means and to receive the
inverted periodic output signal of said inverter means and for
producing a fixed amplitude pulse signal having a pulse width
increasing at the rate of change of said ramp from said second ramp
generator circuit means at the predetermined repetition rate of
said oscillator means until the output signal of said second ramp
generator circuit means reaches the second level and the pulse
width of the pulse signal reaches a predetermined pulse width;
first and second output circuit means connected to receive the
pulse outputs of said first and second pulse width circuit means
respectively and for producing a balanced biphasic constant current
output signal; and
first and second output circuit control means for adjusting the
current amplitude of the output pulses of said first and second
output circuits respectively.
2. The invention of claim 1 wherein said rate control means is
constructed and arranged for altering the repetition rate of said
oscillator means between 3 and 50 pulses per second.
3. The invention of claim 1 wherein said treatment timer control
means is constructed and arranged for establishing the treatment
time of said treatment timer means at 15, 30 or 60 minutes or
continuous.
4. The invention of claim 1 wherein said first cycler control means
is constructed and arranged for setting predetermined "on" time
intervals between 2 and 25 seconds.
5. The invention of claim 1 wherein said second cycler control
means is constructed and arranged for setting predetermined "off"
time intervals between 2 and 50 seconds.
6. The invention of claim 1 wherein said first and second ramp
generator control means are constructed and arranged for varying
the rate of increase of said first and second output ramp circuits
from first to second levels between 0.5 and 8 seconds.
7. The invention of claim 1 wherein said first and second output
circuit control means is constructed and arranged for adjusting the
amplitude of the output pulses between 30 and 100% of a maximum
output current.
8. The invention of claim 7 wherein said first and second output
circuit means are constructed and arranged to provide a maximum
constant output current between 90 and 100 milliamps over a load
impedance range of 100 to 1,000 ohms.
9. A muscle stimulator comprising, in combination:
oscillator means for producing a periodic output signal at a
predetermined repetition rate;
inverter means coupled to receive the output of said oscillator
means, for producing a periodic output signal having a polarity
opposite to that of the periodic output signal produced by said
oscillator means;
treatment timer means for generating a first logic signal after a
predetermined treatment time interval;
cycler means for repetitively producing a second logic signal which
remains at a first logic level for a predetermined "on" time
interval and a second logic level for a predetermined "off" time
interval;
external switch means;
plug means operatively connected to said external switch means;
accessory jack means constructed and arranged for receiving said
plug means and for providing a third logic signal when said plug
means is inserted in said jack means and said external switch means
is in a particular condition or when no plug is inserted in said
jack;
momentary contact switch means for producing a fourth logic signal
when said momentary .[.on.]. .Iadd.contact .Iaddend.switch means is
actuated;
first and second ramp generator circuit means connected to receive
said third and fourth logic signals and for producing first and
second output ramp signals changing from a first to a second level
at first and second predetermined rates, subsequent to receipt of
said first, second, third or fourth logic signals;
first pulse width circuit means coupled to receive the ramp signal
from said first ramp generator circuit means and to receive the
periodic output signal from said oscillator means and for producing
a fixed amplitude pulse signal having a pulse width increasing at a
rate proportional to the rate of change of the ramp signal from
said first ramp generator circuit means at the predetermined
repetition rate of said oscillator means until the output signal of
said .[.second.]. .Iadd.first .Iaddend.ramp generator circuit means
reaches the second level and the pulse width of the pulse signal
reaches a predetermined pulse width;
second pulse width circuit means coupled to receive the ramp signal
from said second ramp generator circuit means and to receive the
inverted periodic output signal of said inverter means and for
producing a fixed amplitude pulse signal having a pulse width
increasing at the rate of change of said ramp from said second ramp
generator circuit means at the predetermined repetition rate of
said oscillator means until the output signal of said second ramp
generator circuit means reaches the second level and the pulse
width of the pulse signal reaches a predetermined pulse width;
and
first and second output circuit means connected to receive the
pulse outputs of said first and second pulse width circuit means
respectively and for producing an output signal.
10. A muscle stimulator comprising, in combination:
oscillator means for producing a periodic output signal at a
predetermined repetition rate;
treatment timer means for generating a first logic signal after a
predetermined treatment time interval;
cycler means for repetitively producing a second logic signal which
remains at a first logic level for a predetermined "on" time
interval and a second logic level for a predetermined "off" time
interval;
external switch means;
plug means operatively connected to said external switch means;
accessory jack means constructed and arranged for receiving plug
means and for providing a third logic signal when said plug means
is inserted in said jack means and said external switch means is in
a particular condition or when no plug is inserted in said
jack;
momentary contact switch means for producing a fourth logic signal
when said momentary .[.on.]. .Iadd.contact .Iaddend.switch means is
actuated;
first and second ramp generator circuit means connected to receive
said third and fourth logic signals and for producing first and
second output ramp signals changing from a first to a second level
at first and second predetermined rates, subsequent to receipt of
said first, second, third or fourth logic signals;
first pulse width circuit means coupled to receive the ramp signal
from said first ramp generator circuit means and to receive the
periodic output signal from said oscillator means and for producing
a fixed amplitude pulse signal having a pulse width increasing at a
rate proportional to the rate of change of the ramp signal from
said first ramp generator circuit means at the predetermined
repetition rate of said oscillator means until the output signal of
said .[.second.]. .Iadd.first .Iaddend.ramp generator circuit means
reaches the signal level and the pulse width of the pulse signal
reaches a predetermined pulse width;
second pulse width circuit means coupled to receive the ramp signal
from said second ramp generator circuit means and to receive the
periodic output signal from said oscillator means and for producing
a fixed amplitude pulse signal having a pulse width increasing at
the rate of change of said ramp from said second ramp generator
circuit means at the predetermined repetition rate of said
oscillator means until the output signal of said second ramp
generator circuit means reaches the second level and the pulse
width of the pulse signal reaches a predetermined pulse width;
first and second output circuit means connected to receive the
pulse outputs of said first and second pulse width circuit means
respectively and for producing an output signal; and
further means operatively coupled to said first and second pulse
width circuit means and said oscillator means for causing said
first and second pulse width circuit means to produce said first
and second output pulse signals alternately at the predetermined
repetition rate of said oscillator means.
11. A muscle stimulator comprising, in combination:
oscillator means for producing a periodic output signal at a
predetermined repetition rate;
inverter means, coupled to receive the output of said oscillator
means, for producing a periodic output signal having a polarity
opposite to that of the periodic output signal produced by said
oscillator means;
treatment timer means for generating a first logic signal after a
predetermined time interval;
cycler means for repetitively producing a second logic signal which
remains at a first logic level for a predetermined "on" time
interval and a second logic level for a predetermined "off" time
interval;
logic means connected to receive said first and second logic
signals and provide a third logic signal when either said first or
said second logic signals are received;
first and second ramp generator circuit means connected to receive
said third logic signal and for producing first and second output
ramp signals changing from a first to a second level at first and
second predetermined rates, subsequent to receipt of said third
logic signal;
first pulse width circuit means coupled to receive the ramp signal
from said first ramp generator circuit means and to receive the
periodic output signal from said oscillator means and for producing
a fixed amplitude pulse signal having a pulse width increasing at a
rate proportional to the rate of change of the ramp signal from
said first ramp generator circuit means at the predetermined
repetition rate of said oscillator means until the output signal of
said .[.second.]. .Iadd.first .Iaddend.ramp generator circuit means
reaches the second level and the pulse width of the pulse signal
reaches a predetermined pulse width;
second pulse width circuit means coupled to receive the ramp signal
from said second ramp generator circuit means and to receive the
inverted periodic output signal of said inverter means and for
producing a fixed amplitude pulse signal having a pulse width
increasing at the rate of change of said ramp from said second ramp
generator circuit means at the predetermined repetition rate of
said oscillator means until the output signal of said second ramp
generator circuit means reaches the second level and the pulse
width of the pulse signal reaches a predetermined pulse width;
and
first and second output circuit means connected to receive the
pulse outputs of said first and second pulse width circuit means
respectively and for producing an output signal.
12. A muscle stimulator comprising:
output enabling means for producing an enabling signal to enable
generation of output pulses by said stimulator;
interval timing means connected to receive the enabling signal
fromm said output enabling means and for generating repetitive
bursts of pulse initiating signals, the time duration of each burst
of pulse initiating signals being a first predetermined time
interval and the time interval separating said bursts of pulse
initiating signals being a second predetermined time interval, said
interval timing means including means for independently adjusting
said first and said second time intervals;
further timing means connected to receive pulse initiating signals
from said interval timing means and for producing output signals
having fixed pulse amplitude and a pulse width increasing from zero
to a selected value over a third predetermined time interval, upon
receipt of the first initiating signal in a burst of pulse
initiating signals; and
an output circuit connected to receive the output signal from said
further timing means and for producing output pulses suitable for
stimulation of muscle tissue. .Iadd.
13. A muscle stimulator comprising, in combination:
oscillator means for producing a periodic output signal at a
predetermined repetition rate;
rate control means coupled to said oscillator means for altering
the repetition rate of said oscillator means;
treatment timer means for generating a first logic signal after a
predetermined treatment time interval;
treatment timer control means coupled to said treatment timer means
for establishing the predetermined treatment time of said treatment
timer means;
cycler means for repetitively producing a second logic signal which
remains at a first logic level for a predetermined "on" time
interval and a second logic level for a predetermined "off" time
interval;
first cycler control means coupled to said cycler means for setting
the predetermined "on" time interval of said cycler means;
second cycler control means coupled to said cycler means for
setting the predetermined "off" time interval of said cycler
means;
external switch means;
plug means operatively connected to said external switch means;
accessory jack means constructed and arranged for receiving said
plug means and for providing a third logic signal when said plug
means is inserted in said jack means and said external switch means
is in a particular condition or when said plug is not inserted in
said jack;
momentary contact switch means for producing a fourth logic signal
when said momentary contact switch means is actuated;
first and second ramp generator circuit means connected to receive
said first, second, third and fourth logic signals and for
producing first and second output ramp signals changing from a
first to a second level at first and second predetermined rates,
subsequent to receipt of either of said first, second, third or
fourth logic signals;
first and second ramp generator control means coupled respectively
to said first and second ramp generator circuit means for
independently altering the rate of change of the output ramp
signals of said first and second ramp generator circuit means;
first pulse width circuit means coupled to receive the ramp signal
from said first ramp generator circuit means and to receive the
periodic output signal from said oscillator means and for producing
a fixed amplitude pulse signal having a pulse width increasing at a
rate proportional to the rate of change of the ramp signal from
said first ramp generator circuit means at the predetermined
repetition rate of said oscillator means until the output signal of
said first ramp generator circuit means reaches the second level
and the pulse width of the pulse signal reaches a predetermined
pulse width;
second pulse width circuit means coupled to receive the ramp signal
from said second ramp generator circuit means and to receive the
periodic output signal of said oscillator means and for producing a
fixed amplitude pulse signal having a pulse width increasing at the
rate of change of said ramp from said second ramp generator circuit
means at the predetermined repetition rate of said oscillator means
until the output signal of said second ramp generator circuit means
reaches the second level and the pulse width of the pulse signal
reaches a predetermined pulse width;
first and second output circuit means connected to receive the
pulse outputs of said first and second pulse width circuit means
respectively and for producing a balanced biphasic constant current
output signal; and
first and second output circuit control means for adjusting the
current amplitude of the output pulses of said first and second
output circuits respectively. .Iaddend. .Iadd.
14. The invention of claim 13 wherein said rate control means is
constructed and arranged for altering the repetition rate of said
oscillator means between 3 and 50 pulses per second. .Iaddend.
.Iadd.15. The invention of claim 13 wherein said treatment timer
control means is constructed and arranged for establishing the
treatment time of said treatment timer means at 15, 30 or 60
minutes or continuous. .Iaddend.
.Iadd.16. The invention of claim 13 wherein said first cycler
control means is constructed and arranged for setting predetermined
"on" time intervals between 2 and 25 seconds. .Iaddend. .Iadd.17.
The invention of claim 13 wherein said second cycler control means
is constructed and arranged for setting predetermined "off" time
intervals between 2 and 50 seconds. .Iaddend. .Iadd.18. The
invention of claim 13 wherein said first and second ramp generator
control means are constructed and arranged for varying the rate of
increase of said first and second output ramp circuits from first
to second levels between 0.5 and 8 seconds. .Iaddend. .Iadd.19. The
invention of claim 13 wherein said first and second output circuit
control means is constructed and arranged for adjusting the
amplitude of the output pulses between 30 and 100% of a maximum
output current. .Iaddend. .Iadd.20. The invention of claim 19
wherein said first and second output circuit means are constructed
and arranged to provide a maximum constant output current between
90 and 100 milliamps over a load impedance range of 100 to 1,000
ohms. .Iaddend. .Iadd.21. A muscle stimulator comprising, in
combination:
oscillator means for producing a periodic output signal at a
predetermined repetition rate;
treatment timer means for generating a first logic signal after a
predetermined treatment time interval;
cycler means for repetitively producing a second logic signal which
remains at a first logic level for a predetermined "on" time
interval and a second logic level for a predetermined "off" time
interval;
external switch means;
plug means operatively connected to said external switch means;
accessory jack means constructed and arranged for receiving said
plug means and for providing a third logic signal when said plug
means is inserted in said jack means and said external switch means
is in a particular condition or when no plug is inserted in said
jack;
momentary contact switch means for producing a fourth logic signal
when said momentary contact switch means is actuated;
first and second ramp generator circuit means connected to receive
said third and fourth logic signals and for producing first and
second output ramp signals changing from a first to a second level
at first and second predetermined rates, subsequent to receipt of
said first, second, third or fourth logic signals;
first pulse width circuit means coupled to receive the ramp signal
from said first ramp generator circuit means and to receive the
periodic output signal from said oscillator means and for producing
a fixed amplitude pulse signal having a pulse width increasing at a
rate proportional to the rate of change of the ramp signal from
said first ramp generator circuit means at the predetermined
repetition rate of said oscillator means until the output signal of
said first ramp generator circuit means reaches the second level
and the pulse width of the pulse signal reaches a predetermined
pulse width;
second pulse width circuit means coupled to receive the ramp signal
from said second ramp generator circuit means and to receive the
periodic output signal of said oscillator means and for producing a
fixed amplitude pulse signal having a pulse width increasing at the
rate of change of said ramp from said second ramp generator circuit
means at the predetermined repetition rate of said oscillator means
until the output signal of said second ramp generator circuit means
reaches the second level and the pulse width of the pulse signal
reaches a predetermined pulse width; and
first and second output circuit means connected to receive the
pulse outputs of said first and second pulse width circuit means
respectively
and for producing an output signal. .Iaddend. .Iadd.22. A muscle
stimulator comprising, in combination:
oscillator means for producing a periodic output signal at a
predetermined repetition rate;
treatment timer means for generating a first logic signal after a
predetermined time interval;
cycler means for repetitively producing a second logic signal which
remains at a first logic level for a predetermined "on" time
interval and a second logic level for a predetermined "off" time
interval;
logic means connected to receive said first and second logic
signals and provide a third logic signal when either said first or
said second logic signals are received;
first and second ramp generator circuit means connected to receive
said third logic signal and for producing first and second output
ramp signals changing from a first to a second level at first and
second predetermined rates, subsequent to receipt of said third
logic signal;
first pulse width circuit means coupled to receive the ramp signal
from said first ramp generator circuit means and to receive the
periodic output signal from said oscillator means and for producing
a fixed amplitude pulse signal having a pulse width increasing at a
rate proportional to the rate of change of the ramp signal from
said first ramp generator circuit means at the predetermined
repetition rate of said oscillator means until the output signal of
said first ramp generator circuit means reaches the second level
and the pulse width of the pulse signal reaches a predetermined
pulse width;
second pulse width circuit means coupled to receive the ramp signal
from said second ramp generator circuit means and to receive the
periodic output signal of said oscillator means and for producing a
fixed amplitude pulse signal having a pulse width increasng at the
rate of change of said ramp from said second ramp generator circuit
means at the predetermined repetition rate of said oscillator means
until the output signal of said second ramp generator circuit means
reaches the second level and the pulse width of the pulse signal
reaches a predetermined pulse width; and
first and second output circuit means connected to receive the
pulse outputs of said first and second pulse width circuit means
respectively and for producing an output signal. .Iaddend.
Description
BACKGROUND OF THE INVENTION
Electrical stimulation of various biological systems is known in
the prior art. For example, pain alleviation through nerve
stimulation or motor control through nerve or muscle stimulation
have been successfully demonstrated.
One of the uses for neuromuscular stimulator systems is to provide
muscle stimulation to assist partially disabled stroke vistims in
raising the toe on the affected leg during that portion of the
walking motion where the foot and heel are off the ground. Systems
for accomplishing such stimulation under the control of a heel
switch are shown, for example, in Offner et al U.S. Pat. No.
3,344,792.
An implantable system to correct for foot drop is discussed in
"Developing Clinical Devices for Hemiplegic Stroke Patients
(Revised)" by Edward Schuck, Harry Friedman and others in a paper
originally presented at the Fourth International Symposium on
External Control of Human Extremities, Aug. 28-Sept. 2, 1972, at
Dubrovnik, Yugoslavia.
The improved neuromuscular stimulator of the present invention
provides a stimulator with dual channel capabilities for
simultaneous neuromuscular stimulation at two sites to provide a
more comprehensive treatment device to reduce the amount of time
needed to administer a stimulation treatment program. The variable
on/off cycling capability allows the user to select stimulation
parameters effective for exercising muscles to prevent disuse
atrophy while minimizing muscle fatigue. The optional control of
the device through a remote switch connected to an "accessory" jack
allows for more flexible application of the stimulator to treatment
of varying conditions.
SUMMARY OF THE INVENTION
Briefly described, the apparatus of this invention and its
preferred embodiment comprise a portable neuromuscular stimulation
system for use to provide external electrical stimulus induced
muscle exercise to retard or prevent disuse atrophy and for other
purposes such as the correction of hemiplegic foot drop. The
stimulator provides, on two output channels, alternating pulsed
stimulation signals which are connected to electrodes through
flexible cables. The pulsed signals, when applied, are increased in
intensity at a variable rate until a fixed intensity is reached.
The pulses are applied during an adjustable predetermined
stimulation interval and removed for an adjustable predetermined
resting interval which occurs alternately during a particular
treatment interval which is preset by a treatment timer time
selector. The amplitude limit of the pulse at the output channels
is individually adjustable by the patient within an upper limit
which is independently established by a clinician for each channel
at the time the device is set up for the patient.
The time delay required for the increase of output pulses to their
full selected power may be independently adjusted for each channel
by clinician controls. The pulse rate of the stimulation pulses may
also be established by a clinician control. A patient accessible
control provides a constant train of stimulation pulses when
actuated and an accessory input jack allows the control of pulse
trains from either an external physician controlled switch or from
a heel switch when the stimulator is used to correct hemiplegic
foot drop.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a simplified functional block diagram of the dual channel
neuromuscular stimulator system, according to the present
invention; and
FIG. 2 is a layout of the detailed schematic of FIGS. 2A through 2C
which show the circuitry of the neuromuscular stimulation
system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring first to FIG. 1, there is shown a simplified block
diagram of the dual channel neuromuscular stimulator system of the
present invention. The overall unit 10 has a pair of output jacks
12 and 14 which can be connected to suitable stimulation
electrodes, such as Medtronic Conductive Carbon Electrodes #3791,
3793, 3794 or 3795, through normal plug-in cables such as Medtronic
#3781 cable. The electrodes are affixed to the skin over the muscle
and nerve tissue to be stimulated using Neuromod.RTM. TENS
electrode gel and tape patches for the selected carbon
electrode.
The circuitry providing the excitation at output jacks 12 and 14 is
identical for channels 1 and 2. Each channel has a constant current
output circuit 16 and 18. Individual patient adjusted amplitude
controls 20 and 22 provide an adjustment of stimulation pulse
amplitude which is accessible to the patient. Additionally, a
physician or clinician controlled amplitude limit adjustment 24 and
26 is also provided for each channel. The clinician controls are
located under a protective cover in the device to limit their
accessibility to the patient. The physician accessible limit
controls 24 and 26 allow the physician to establish an upper limit
for stimulation amplitude as well as allowing the patient adjusted
amplitude controls 20 and 22 to be adjustable over the most
desirable part of the range of operating amplitudes.
The drive signals 28 and 30 to the output circuits 16 and 18 are
provided by identical channel 1 and channel 2 pulse width circuits
32 and 34. The pulse width circuits are driven by input signals 36
and 38 which are supplied respectively by a rate oscillator 40 and
a phase inverter 42 which receives its input signal 44 from rate
oscillator 40. Rate oscillator 40 has a physician controlled
adjustment means 46 to alter the oscillation rate. In the preferred
embodiment shown, the pulse rate is adjustable between 3 and 50
pulses per second.
Additional inputs to the pulse width circuits 32 and 34 are
provided by pulse width ramp generation circuits 48 and 50. The
ramp circuits 48 and 50 are adjustable by clinician controlled ramp
time adjustment means 52 and 54, respectively. The pulse width ramp
circuits 48 and 50 also receive inputs from a momentary "on" switch
56 which is also referred to herein as a "constant stimulation"
actuating switch. Further inputs to the pulse width ramp circuits
48 and 50 are provided through accessory jack 58. The accessory
jack may be connected to an external switch such as a physician
controlled switch which may be used during calibration of the
stimulator to apply pulses independent of the status of separate
"on" and "off" time controls discussed below. Signals controlling
the pulse width ramp circuits from the treatment timer 60 and
on/off cycler 62 are also passed through the accessory jack 58 as
shown more fully in the detailed schematic of FIGS. 2A through
2C.
Treatment timer 60 receives an input from a patient control 64 to
set the length of the treatment time and shut down the operation of
the stimulator after the selected treatment time has elapsed. The
on/off cycler 62 provides for intermittent operation of the
circuitry during a treatment to apply pulses in bursts having a
predetermined time duration and to suppress the pulse output during
a predetermined "off" time or rest interval as established by
physician actuated adjustment controls 66 and 68. The treatment
timer provides for treatment time of 15, 30 or 60 minutes or
continuous operation while the on/off cycler provides alternative
stimulation and resting intervals of 2 to 25 seconds and 2 to 50
seconds, respectively.
Referring now to FIGS. 2A through 2C, there is shown a detailed
schematic diagram of the dual channel neuromuscular stimulator
system according to the present invention. The broken line boxes in
FIGS. 2A through 2C correspond generally to the similarly numbered
boxes in the functional block diagram of FIG. 1. Box 72 encloses
power source circuitry not explicitly shown in FIG. 1.
The details of construction and operation of the various block
elements shown in FIG. 1 and FIGS. 2A through 2C is described
below.
The dosage timer 60 utilizes as the principal timing means a
14-stage binary CMOS counter U3 manufactured by Fairchild and
others as a model 4020. The numbers at the outside of the box U3
denote the manufacturer's pin designations for the various
terminals and the lettering on the inside of the box indicates the
functional description of the various U3 terminals utilized in
dosage timer 60. The three outputs from the counter U3 at pins 1, 2
and 3 are from the 12th, 13th and 14th counter stages,
respectively, and are connected to diodes CR4, CR5 and CR6. The
input to U3 at terminal 10 is provided by a Schmitt trigger circuit
U2A utilizing one element of a Schmitt trigger module such as a
model 40106 unit manufactured by RCA, National Semiconductor and
others which contains six Schmitt triggers. The adjustable feedback
resistor R3 and timing capacitor C3 operate to establish the
frequency of Schmitt trigger U2A as an oscillator to provide a
clock signal to the input to U3. In a preferred embodiment of the
stimulator, the clock signal is selected to provide outputs at
stages 12, 13 and 14 of the binary counter at 15, 30 and 60
minutes, respectively. By selecting the appropriate output from
counter U3, it is then possible to obtain a logic signal at either
15, 30 or 60 minutes for use in terminating the treatment.
The treatment timer is reset as the unit is initially powered up by
the voltage divider comprised of capacitors C1, diode CR1 and
resistor R1. When the "power on" switches S1 and/or S2 are closed,
the +V voltage is applied to the various circuits to which it is
connected and a regulated V1 voltage is developed across CR3. In
the preferred embodiment shown, S1 and S2 are included in the
patient amplitude controls 20 and 22, respectively. Capacitor C2 is
charged almost instantaneously through limiting resistor R2 and
provides a filtering effect for the regulated voltage V1 across
CR3. When V1 is applied to C1 as either S1 or S2 is closed to
energize the stimulator, C1 begins with no stored voltage so that
the charging current passing from V1 to ground through CR1 and R1
develops a positive voltage across R1 to apply a reset signal to
terminal 11 of U3. After C1 is fully charged, the charging current
drops to zero and thereby removes the reset signal to allow the
input clock signal at terminal 10 of U3 to begin the counting
operation.
A reset signal can also be applied to the dosage counter U3 by
conductor 76 which is connected to terminal 86 of a four-position
slide switch 64 which provides the adjustment to select the desired
treatment time. Slide switch 64 has terminals 78, 80, 82, 84 and
86. In the first position, the movable conductive element 87 in the
slide switch shorts terminals 78 and 80 together; in the second
position it shorts terminal 80 to 82; and, in a third position,
shorts terminal 82 to 84 and finally, in the fourth position,
shorts terminal 84 to terminal 86. In the first position, a
15-minute time interval is selected, in the second, a 30-minute
time interval, in the third, a 60-minute time interval and, in the
fourth position, because terminal 84 is connected to regulated
supply at V1, a positive voltage is connected to the reset input of
timer U3 to cause the stimulator to operate in a continuous mode
since the treatment timer counter has been disabled by application
of constant voltage to its reset terminal. It is particularly
convenient to have the continuous operating mode switch position
available when the physician is adjusting the various physician
controlled parameters of the stimulator to avoid having the
stimulator shut off by the treatment timer 60 while adjustments are
being made. In the schematic in FIG. 2A, terminals 78 and 80 are
shown shorted together, representative of the switch being in
position 1 selecting 15-minute operation. The other switch
positions for wiper 87 are shown in phantom or dotted line form in
FIG. 2A.
When the count in counter U3 reaches the 12th stage of the 14-stage
counter, a positive voltage is applied through CR4 to terminal 78,
through the switch contact to terminal 80 and through CR7 to the
input at terminal 13 to the Schmitt trigger oscillator U2A to stop
operation of the oscillator after the desired time has been
reached. This is done for the three time intervals of 15, 30 and 60
minutes so that the "end of treatment command" signal will not be
erroneously removed by the count advancing to the next stage in the
14-stage binary counter U3.
The output signal from the selected 12th, 13th or 14th stage of the
14-stage binary counter U3 is connected through diode CR10 and
normally closed switch contact of accessory jack J5 to the
remainder of the circuit where it is used, as described below, to
disable the application of stimulation pulses by the circuitry
after the desired treatment time has elapsed. The normally closed
contact 90 in accessory jack J5 is opened when an accessory switch
is used to bypass the treatment timer.
In addition to the treatment timer reset pulse which is generated
by C1, CR1 and R1 when the system is powered up, a reset signal can
also be applied to the treatment timer counter by switching the
selector switch 64 to the fourth position to bridge contacts 84 and
86 and apply the voltage V1 directly to the reset input terminal 11
of the dosage timer. When the switch is set in this position, the
stimulation circuit is in continuous operation at the selected
pulse rate and at the selected on and off cycle time and the
treatment time is not being measured by the counter U3. Of course,
the resetting of counter U3 removes any positive output signals
from the 12th, 13th and 14th binary stages to allow the Schmitt
trigger oscillator U2A to resume operation at the beginning of its
timing cycle.
In addition to the treatment timer 60, the circuit 10 includes a
cycle timer 62, the details of which are shown in FIG. 2B. The
cycle timer 62 establishes the "on" or stimulation and "off" or
resting time intervals which alternate during the selected
treatment time in accordance with clinician adjustable controls 66
and 68 which are variable resistors appearing in the circuit of the
cycle timer 62 as shown in FIG. 2B.
The variable resistor 66 is in the feedback circuit of Schmitt
trigger U2D in series with a calibration resistor R10. In order to
have Schmitt trigger U2D operate as an oscillator, a capacitor C5
is connected from its input terminal 1 to ground. The output of the
Schmitt trigger oscillator U2D is passed through diode CR13 to
terminal 10 of U4 which is the input to a 14-stage binary counter
of the same type as U3. Counter U4 is reset when a positive voltage
is applied to reset terminal 11. A reset signal is provided by the
capacitor C1 resistor R4 voltage divider when the circuit is
powered up. The output of U4 at the 14th stage of the binary
counter at pin 3 is connected through diodes CR9 and OR'ed with the
end of treatment command signal from treatment timer 60 and the
resultant signal is passed through resistor R43 to indicator
circuit 70. The signal is also provided, as indicated above,
through J5 and resistor R43 and diode CR2 to inhibit generation of
pulses when either the selected time for the treatment timer has
elapsed or when the stimulator is in the "off" time interval.
The "off" timer is mechanized in FIG. 2B utilizing Schmitt trigger
circuit U2B. The feedback resistors include a calibration resistor
R7 and the physician controlled resistor 68. Capacitor C4 causes
the circuit to oscillate in the same manner as the "on" timer, but
at a slower rate to allow for the longer off intervals utilized in
the preferred embodiment. The output signal of oscillator U2B at
terminal 8 is connected through diode CR12 to the input to counter
U4.
Oscillators U2B and U2D do not operate at the same time. The
circuitry comprised of diode CR14, diode CR11 and Schmitt trigger
U2C operates as a toggle to enable either U2B or U2D to oscillate
at any one time. U2C is connected as an inverter. When the
stimulation device is in the "on" cycle, pin 3 of U4 is at a low
voltage so that the U2D oscillator is operating as the binary
counter U4 counts until the output of binary stage 14 at pin 3
switches to a high voltage. When that voltage switches, it shuts
down the stimulator by feeding the positive voltage through CR9 and
jack J5 in the same way that the end of treatment command from
treatment timer 60 is fed. The high voltage at pin 3 of U4 feeds
through CR14 to stop the operation of oscillator U2D. That high
voltage is also conducted through resistor R44 to U2C which inverts
it to remove the high logic signal that was conducted through CR11
to keep oscillator U2B stopped. Thus, U2B starts to operate when
U2D is shut down. By adjustment of the operating frequencies of U2D
and U2B, the on and off times of the preferred embodiments shown
can be adjusted over ranges of 2 to 25 and 2 to 50 seconds,
respectively.
The constant stimulation momentary on switch block 56 has a switch
designated S3 in FIG. 2A. When switch S3 is actuated, it connects
the cathode of CR8 to ground. This inhibits signals coming from
jack J5, preventing output circuit to turn off. The treatment timer
60 and the cycle timer 62 are inhibited from shutting the circuit
off during the time that the momentary contact switch S3 is
closed.
The closure of switch S3 also applies a ground to the input of U2C
which puts a high logic signal on the output of U2C to stop
oscillator U2B. This operational feature allows oscillator U2D to
keep running until U4 reaches the end of its time cycle so that
when the pressure on the constant stimulation button S3 is removed,
the cycle time is in the "off" position and at the beginning of the
"off" cycle. This is an important operational feature because after
continued stimulation under control of the constant stimulation
switch has been applied to a muscle group, it is extremely
desirable to allow the muscle to recover in a nonstimulated
condition. Allowing the "on" cycle timer to continue to run to
bring the circuit back into the beginning of the "off" cycle during
the time that constant stimulation is applied accomplishes this
desirable objective in the preferred embodiment of the stimulator
shown.
It should also be noted that actuation of the constant stimulation
button S3 does not reset the treatment timer 60.
The output signal at terminal 3 of counter U4 is connected through
J5 to the cycler indicator lights 70. The signal passes through
resistor R5 to the base of NPN transistor Q1 which has its base
connected to ground through resistor R41. The collector of Q1 is
connected to the base of Q2 through resistor R12. A green light
emitting diode CR15 is connected to the collector of Q1 while a red
LED CR16 is connected to the collector of Q2. The anodes of CR15
and CR16 are connected through a current limiting resistor R11 to
the unregulated supply voltage +V. The emitters of Q1 and Q2 are
tied together and connected to the collector of NPN transistor Q9
which receives an input signal through R42. Either Q1 or Q2 is
turned on, depending upon whether the output of U4 is in a high or
low condition. Q9 is turned on for each half cycle of the output of
rate oscillator 40. The LEDs thus operate to indicate whether the
stimulation is "on" or "off". During the "on" cycle or when S3 is
pushed for constant stimulation, the red light of CR16 will come
on. During the "off" cycle or once the treatment timer shuts the
device down, the green light of CR15 comes on. Since Q9 is turned
on and off at the rate of the rate oscillator, the light emitting
diodes CR15 and CR16 are blinked at a rate corresponding to the
rate of the oscillator and the power consumption to drive the
indicators is substantially reduced. If the rate of oscillator 40
is set at a very low rate, the blinking is visible to the user's
eye.
The signal from the output of timers U3 and U4 after passing
through the normally closed contacts 90 of J5 is conducted through
resistor R43, CR2, conductor 93 and resistor R16 to the base of NPN
transistor Q3. The base of Q3 is connected to ground through R15.
The collector of Q3 is connected through R22 to the base of Q8. The
emitter of NPN transistor Q8 is connected to the regulated supply
+V1. The base of Q8 is connected to the regulated supply +V1
through resistor R45 and the collector of Q8 is connected through
R23 to diodes CR26 and CR23 at the inputs of identical channel 1
and channel 2 ramp circuits 48 and 50, respectively, as shown in
FIG. 2C. The detailed circuitry of pulse width circuits 32 and 34
are also identical. Accordingly, it is necessary only to describe
the operation of the channel 1 output circuitry since the channel 2
output circuitry is essentially identical.
When the U3 or U4 timers switch to a positive signal, that signal
charges capacitor C9 of ramp circuit 48 rapidly through resistor
R23 which has a low impedance. The positive voltage applied at
noninverting input terminal 5 of U1C produces a positive voltage at
the output terminal 7 of U1C which is connected through resistor
R25 to the noninverting input of U1D in the channel 1 pulse width
circuit. Thus, when a positive voltage is applied to CR26, a
positive signal is applied at the input of pulse width circuit 32
which, as described below, turns off the channel 1 output. When the
positive signal holding channel 1 off is removed from the anode of
CR26, capacitor C9, which had been previously charged to a high
logic signal, begins to discharge through the series combination of
adjustable resistor 52 and fixed resistor R18.
Since U1C is connected as a voltage follower, the positive output
of U1C gradually diminishes. The diminishing ramp signal from the
output of ramp circuit 48 is summed in the pulse width circuit 32
with a rate signal on conductor 36 produced by rate oscillator 40,
the operation of which is discussed below.
The square wave rate signal on conductor 36 is passed through
capacitor C10 to the wiper of variable resistor R38 and through
resistor R27 to the noninverting input terminal 3 of U1D. A diode
CR25 has its anode connected to ground and its cathode connected to
pin 3 of U1D. The values of R38, R27 and C10 are selected to give a
time constant which, when applied to the square wave signal at the
output of oscillator 40, produces a nominal 225 microsecond pulse
width for the output pulses. The pulse width of the drive signal on
conductor 28 is inversely dependent upon the magnitude of the ramp
input to U1D produced by the ramp circuit 48. As the output of U1C
follows C9 to zero, +V1 divides across R26 and R25 to ground
through U1C to provide a fixed bias to pin 2 of U1D.
The signal on conductor 28 is connected to the output circuit 16 of
channel 1. The signal is an increasing pulse width signal beginning
from a very narrow signal when the positive voltage is removed from
the anode of CR26 and increasing to the full nominal pulse width
after the ramp signal at the output of the ramp circuit 48
decreases to zero in accordance with the setting of ramp adjustment
control 52. As the output of U1C follows C9 to zero, +V1 divides
across R26 and R25 to ground through U1C to provide a fixed bias to
pin 2 of U1D. The leading edge of the pulse occurs at intervals
determined by the square wave signal produced by oscillator 40 so
the leading edges of the drive pulses on conductor 28 occur at a
fixed pulse rate.
Rate oscillator 40 is based on Schmitt trigger U2E and its
adjustable feedback resistors R13 and 46 and timing capacitor C6.
The drive signal to channel 1 is inverted by Schmitt trigger U2F so
that the identical drive circuitry of channels 1 and 2 is not in
the "on" condition at the same time. This is necessary to avoid
undesirable overloading of the power supply. Cells BT1, BT2 and BT3
provide the power for the device. Capacitors C11 and C12 are large
capacitors used to facilitate driving the output current. They are
back-to-back to prevent damage due to improperly installed
batteries.
Because the output circuits 16 and 18 are identical, only the
channel 1 output circuit 16 is described in detail. The drive
signal on conductor 28 is passed through a variable calibration
resistor R28, the physician amplitude control 24 and the drive
signal for Q4 is taken from the wiper of the patient adjustment
amplitude control 20. The winding of potentiometer or a variable
resistor 20 is connected to the base of a grounded emitter open
collector NPN transistor Q11 to provide temperature and
base-emitter voltage compensation for Q4. The collector of Q4 is
connected to the base of PNP Darlington transistor pair Q5 which
has its emitter connected to the +V supply. The Darlington base
junction is also connected to the positive supply through R33. The
collector of Q5 is connected through the primary winding of
isolation transformer T1 and a current measuring resistor R31 to
ground. R31 has an extremely low resistance and serves as a current
sensor to force Q5 to drive a constant current in the primary of
T1.
The current feedback is obtained as follows. The base-emitter
voltage of Q4 and Q11 are matched so that the voltage from control
20 is applied to R31 to drive a current therein proportional to the
setting of 20. Thus, the T1 primary current is fixed at a selected
current. T1 acts as a current transformer to produce a constant
current output for load impedance from 100 to 1,000 ohms.
A flyback diode CR17 suppresses the inductive surge voltage across
the primary winding of transformer T1 when Q5 shuts off at the
completion of a pulse.
The secondary winding of transformer T1 is connected to output
terminals 12. Zener diode CR19 is a safety diode to prevent the
voltage across output terminals 12 rising to an excessive value if
the output impedance across terminals 12 is extremely high due to a
loose electrode or some similar kind of open circuit condition.
Diode CR18 is used to keep CR19 from forward conducting during the
negative or biphasic portion of the pulse, thus maintaining a zero
net DC output to the patient. The transformer produces a balanced
biphasic rectangular waveform with a zero net DC component to
minimize the possibility of skin rash developing from
stimulation.
The device is operated as follows. Fresh, fully-recharged batteries
BT1, BT2 and BT3 are installed. Both amplitude controls 20 and 22
are set with S1 and S2 in the off position and at minimum
resistance and the clinician or physician operated amplitude limit
controls 24 and 26 are set at initially 50% of appropriate levels.
These and other clinician controls are set to produce minimal
muscle fatigue while comfortable to the patient. The on and off
time controls are also preset. Generally, on off-time of twice the
on-time will avoid fatigue and a ramp time of approximately two
seconds will produce a good, comfortable contraction. A selected
pulse rate of 30-35 pulses per second will produce a fused
contraction with minimal fatigue. If the amplitude settings of
controls 24 and 26 are insufficient to produce an adequate muscle
contraction, then they may be adjusted upward until a good
contraction is achieved.
After the clinician controls are initially adjusted, the cables and
electrodes are connected at jacks 12 and 14 and the electrodes are
attached to the patient. The treatment time switch 64 is set in the
continuous position and the constant stimulation button S3 is
depressed while the patient amplitude adjustments 20 and 22 are
advanced to produce a fused, but comfortable, contraction. If an
adequate contraction is not achieved, even when the amplitude knobs
are set to their maximum setting, the controls are returned to the
minimum setting and the physician amplitude controls 24 and 26 are
advanced by another increment before the patient adjusted amplitude
controls 20 and 22 are again adjusted. When an adequate contraction
is achieved, the constant stimulation S3 is released and the
treatment time switch is set for the desired time interval,
allowing treatment to begin.
* * * * *