GB2099705A - Pulse generator for pain blocking bandage - Google Patents

Abstract

A self-contained, portable, pain blocking bandage has a pulse generator 48, 50, 52 which applies repetitive pulses to an output stage 58 via a pulse buffer and shaper 54, the output stage including a positive feedback circuit 66, 68 which causes the patient to receive a burst 78 of multiple pulses for each pulse produced by the pulse generator 48, 50, 52. Adjustment of a resistor 66 in the feedback circuit varies the number of pulses in each burst. The output amplitude is selected by a potentiometer 74 and is indicated to the patient by a piezoelectric audio transducer 88. As the bandage is placed on the skin a switch 18 is actuated so that a transistor 46 turns on to apply power to the pulse generator and following circuit stages. <IMAGE>

Description

SPECIFICATION Pulse generator for pain blocking bandage This application relates to devices, commonly known as pain blocking bandages, which are applied to an injured body portion for blocking or masking pain arising from an injury, and in particular to such pain blocking bandages which are self-contained, i.e., which do not require any cables or wires for connection to external power sources, pulse signal sources, or other signal generators, etc.

Background of the Invention Reference may be made to the following United States patents of interest: 4,014,347; 4,105,017.

There are presently available devices termed "Pain Blocking Bandages" which are selfcontained units for direct application to an injured body portion in treating or modifying pain. Such devices modify pain by transmitting small, electrical signals through the skin to the underlying nerves in accordance with a technique known as "transcutaneous electrical nerve stimulation", commonly known as TENS. It has been found that the electrical currents somehow block or mask transition of pain signals by the peripheral nerves immediately adjacent the injured body portion.

In a known self-contained pain blocking bandage utilizing TENS, the bandage includes a flexible housing containing a power source and a pulse generator feeding an output pulse circuit for generating low current, repetitive electrical pulses of fixed amplitude and repetition rate to respective flat electrodes provided on the housing bottom. A flexible, segmented electrolyte gel containing member is placed intermediate the electrodes on the housing bottom and the patient's skin to enable the electrical pulses to conductively flow from one electrode and an associated electrolyte segment, through the patient's skin, back to another electrolyte segment and the associated second electrode.These devices are small, portable, relatively inexpensive units as opposed to other currently existing TENS units which require the attachment of wires, cables, or electrodes to precise body locations and which require setting of the pulse rate, pulse amplitude and pulse frequency in the external pulse signal generator. In contrast, the smaller, and less expensive pain blocking bandage incorporates an internal, self-contained power supply and pulse generator. Such self-contained units can be used by any person without requiring any special training in that the pulse rate, pulse amplitude and pulse frequency normally are fixed and therefore nonadjustable.Generally, such pain blocking devices provide repetitive pulses at a rate about 100 pulses per second with a pulse width of about 100 microseconds and a pulse amplitude of about 20 volts, peak to peak, for a small bandage and up to about 80 volts, peak to peak, for a larger bandage.

In certain treatment situations, it is desired to apply more energy during the pulsed portion of the treating signal. With the larger types of TENS units, this can be easily carried out by widening the pulse width, increasing the pulse amplitude, or increasing the power source.

Reference may be made for instance to the aforementioned U.S. Patent No. 4,105,017 wherein there is described a two mode unit in which in a second mode there is provided a repetitive burst of multiple pulses in which the burst width is significantly greater than the normal, single pulse width supplied in the first mode. There is described therein the desirability of such a wider burst of multiple pulses to attain certain efficacious tissue treatment. A burst of multiple pulses as opposed to a single pulse is provided by utilizing gating circuits in which two oscillators are used, one at a low frequency, and another at a higher frequency.

It is now desired to provide an increase in the energy per treatment pulse in the smaller, portable self-contained pain blocking bandage type TENS devices. In such an application, the two oscillator gating approach is not a viable procedure since it does not provide increased energy in the pulse burst, and instead reduces the effective energy, increases the apparatus' costs and requires additional space.

Thus, it is specifically desired to provide an economical circuit which could apply repetitive bursts of multiple pulses at the same repetition rate as prior pain blocking bandage devices. If attained, this would supply the desired increase in energy delivered per burst without either changing the power source, the pulse width, the pulse amplitude or the repetition rate commonly utilized in existing pain blocking bandages.

Summary of the Invention A self-contained, portable bandage adapted to be applied adjacent a painful portion of a patient's body, including pulse generating circuit means with a pulse output driver for generating low current, repetitive electrical pulses within the patient's body to block the pain arising from the painful portion, and wherein there is provided feedback means coupled to the pulse output driver for providing repetitive bursts of multiple pulses to increase the amount of energy available to be applied to the patient during the pulses. The selfcontained bandage includes a power source, such as a battery, and the repetitive electrical pulses are of a fixed repetition rate. The feedback means comprises a positive feedback circuit such as a series connected resistor and capacitor connected across the pulse output driver.The repetitive bursts of multiple pulses are at the same repetition rate as the fixed repetition rate.

Variable amplitude means are provided coupled to the output circuit to enable the amplitude of the repetitive bursts of multiple pulses to be adjusted by the patient. Audio means are also coupled to the variable amplitude means so that an audio signal is provided corresponding to the amplitude of the repetitive burst of multiple pulses in response to the set position of the variable amplitude means.

The improved self-contained bandage in accordance with the present invention advantageously provides the desired repetitive bursts of multiple pulses in an entirely self contained unit to enable a patient to utilize this type of treatment pulse signal in the TENS mode without having extraneous power supply wires or signal connecting cables dangling from the bandage. In addition, the patient need only adjust the pulse amplitude to his satisfaction without requiring special training to set the pulse width or the repetition rate.

Brief Description of the Drawings The features of this invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with its object and the advantages thereof may be best understood by reference by the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements in the several figures and in which:: Figure 1 is a perspective view illustrating a selfcontained bandage applied directly onto a painful portion of a patient's body and incorporating the principles of the present invention; Figure 2 is a block diagram illustrating the electrical circuit with the feedback means provided in the pain-blocking bandage in Figure 1 in accordance with the present invention; Figure 3 is a detailed electrical circuit schematic of a feedback means, variable amplitude and audio means incorporated in a pain-blocking bandage in accordance with the principles of the present invention to provide repetitive burst of multiple pulses; Figure 4 is a schematic diagram illustrating the repetitive bursts of multiple pulses provided in accordance with the principles of the present invention.

Detailed Description Referring now to Figure 1, there is illustrated a self-contained pain blocking bandage 10 adapted for application to an injured portion of a patient's body such as the forearm 12. Pain blocking bandage 10 includes a flexible housing with a compartment 14 containing a portable power source, such as a battery, a compartment 16 containing a pulse generating circuit powered by the battery, an on/off switch 18 and a dial 20 for setting the desired pulse amplitude of the output pulse signals. Compartments 14 and 16 are integral with a base 22 containing respective flat electrodes on the bottom surface thereof facing the patient's body. As is well known in the prior art, a flexible electrolyte pad containing segmented gel portions is placed intermediate the base electrodes and the patient's body.The combination is then held in place by suitable strips of tape 24 placed over base portion 22.

Referring now to Figure 2, there is illustrated in block diagram form an electrical circuit 26 which is included within compartment 16 and provides repetitive bursts of multiple pulses in selfcontained bandage 10 in accordance with the principles of the present invention. A pulse generator 28 supplies repetitive single pulses 30 which are then coupled through pulse buffer and shaper means 32 to a pulse output circuit 34. A positive feedback circuit 36 is coupled across the pulse output circuit with the results being repetitive bursts of multiple pulses 38 whose amplitude is adjusted through variable amplitude means 40 for coupling of the repetitive bursts through terminals A and B to respective electrodes located underneath base 22.A transducer 42 responds to variations in the amplitude to provide a corresponding audio level indicative of the instantaneous amplitude of the repetitive burst 38 as set by the variable pulse amplitude means 40.

Figure 3 sets forth in schematic form the electrical circuit corresponding to the block diagram Figure 2 with the exception of the input trigger stage 44 shown in Figure 4. As an alternative to the on/off switch 18 to initiate pulse generator 28, trigger circuit 44 is included with an input connected through terminal C to an additional, respective electrode on the bottom of base 22. In the circuit of Figure 3, as the bandage 10 is placed on the skin, trigger circuit 44 is initiated by the actuation of the on/off switch 1 8 placed in series with the power supply to trigger circuit 44 to initiate pulses 30.

In Figure 3, when trigger circuit 44 is activated, transistor 46 is driven into full conduction so as to place the battery power source across a series resistor 48 and capacitor 50 which acts as an RC time constant circuit setting the oscillation frequency or repetition rate in the final pulse signal. Resistor 48 and capacitor 50 as well as unijunction transistor 52 provides pulse signal 30 with the repetition rate below 150 pulses per second with a pulse width between 50 400 microseconds and a pulse amplitude between a minimum of zero volts, peak to peak, and a maximum of about 60-80 volts, peak to peak.

A PNP buffer and shaper circuit including transistor 54 optimizes pulse 30 as to pulse width and amplitude and feeds the corresponding output pulses through resistor 56 and a pulse output circuit including an NPN transistor 58 and output transformer 60. Output transformer 60 includes a primary winding 62 and a center-tapped secondary winding 64. Positive feedback circuit 36 in the illustrated embodiment of the invention shown in Figure 3 comprises series connected resistor 66 and capacitor 68 connected from the center-tapped terminal 70 to the input terminal 72. Potentiometer 74 is coupled across the output transformer secondary, with potentiometer 74 connected to terminal A.

It has been found that by adjusting potentiometer 66, pulse bursts containing 1,2 or 3 pulses can be obtained in the output at terminals A, B. As an example, Figure 4 illustrates a repetitive burst of 3 pulses at the same repetition rate as the rate determined by a pulse train containing pulse signal 30 set by pulse generator 28. As shown in Figure 4, each burst 78 contains a combination of pulses 80, 82, 84 separated by a quiescent level 86.

The pulse amplitude output is adjusted by varying the position of potentiometer arm 76. A piezoelectric crystal pager 88 connected across the variable output provides an audio indication of the instantaneous pulse output amplitude. Thus, as the output pulse amplitude is adjusted, piezoelectric pager 88 varies in output level i.e., the pager output amplitude level variations being higher for higher pulse amplitude output and being correspondingly a lower output amplitude level for lower pulse amplitudes. Thus, the user has a direct correlation between the audio loudness and the pulse output amplitude. Bypass capacitor 90 is connected across the power source.

In a constructed embodiment of the invention as illustrated in Figures 3 and 4, a repetitive burst of multiple pulses was obtained at a repetition rate of about 70 Hz; with a burst 78 width of about 1 60 microseconds; and a burst amplitude being adjustable from about zero volts to about 60-80 volts, peak to peak.The components to obtain such a pulse signal consisted of the following (with reference to Figure 3); resistor 11, 50K ohms; resistor 1 3, 200K ohms; resistor 48, 68K ohms; resistor 1 5, 1 00 ohms; resistor 17, 220 ohms; resistor 19, 5.6K ohms; resistor 21, 47 ohms; resistor 23, 1 K ohms, resistor 56, ÓK ohms, potentiometer 66, 50 ohms, potentiometer 74, 5K ohms; capacitor 50, 0.1 Mfd.; capacitor 90, 10 Mfd., electrolytic; capacitor 68, 0.1 Mfd.; transistor 46, MPA A20; unijunction transistor 52, 2N2646 or 2N487 1; transistor 54, 2N3906; transistor 58, MPA Al 4. Output transformer 60 consisted of an audio transformer having an audio frequency primary winding impedance of 8 ohms and a secondary winding audio frequency impedance of 1K ohms, with the DC primary resistance of 0.95 ohm and a DC secondary resistance of 6.5 ohms. Piezoelectric pager 88 comprises a commercial item made by Murata, 7BB-20-6AO.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.

Claims (12)

1. A self-contained bandage adapted to be applied adjacent a painful portion of a patient's body, said bandage comprising circuit means for generating low current, repetitive electrical pulses within the patient's body to block the pain arising from the painful portion, characterized by feedback means coupled to said circuit means for providing repetitive bursts of multiple pulses to be applied to the patient during said pulses.

2. A self-contained bandage according to claim 1, wherein said feed back means comprises positive feedback means.

3. A self-contained bandage according to claim 2, wherein said positive feedback means includes a series connected resistor and capacitor.

4. A self-contained bandage according to claim 3, wherein said series connected resistor is variable to vary the amount of positive feedback and the resulting number of multiple pulses within said repetitive bursts.

5. A self-contained bandage according to claim 1, including means for varying the amplitude of said repetitive bursts of multiple pulses.

6. A self-contained bandage adapted to be applied adjacent an injured portion of a patient's body, said bandage comprising a power source and circuit means having a pulse generator and an output pulse circuit for generating low current, repetitive electrical pulses of fixed amplitude and repetition rate within the patient's body to block the pain arising from said injury, characterized by feedback means coupled to said circuit means for providing repetitive bursts of multiple pulses, said bursts being at the same repetition rate as said fixed repetition rate; variable amplitude means coupled to the output of said circuit means for varying the amplitude of said repetitive bursts of multiple pulses; and audio means coupled to said variable amplitude means for providing an audio signal corresponding to the amplitude of said repetitive burst of multiple pulses in response to said variable amplitude means.

7. A self-contained bandage according to claim 6, wherein said feedback means comprises a positive feedback circuit connected across said output pulse circuit.

8. A self-contained bandage according to claim 7, wherein said positive feedback circuit includes a series connected resistor and capacitor.

9. A self-contained bandage according to claim 6, wherein said output pulse circuit includes a transformer having a center-tapped output secondary winding, means connecting said feedback means from said center tap and across said output pulse circuit.

10. A self-contained bandage according to claim 9, wherein said variable amplitude means includes a variable potentiometer connected across said output secondary winding.

11. A self-contained bandage according to claim 10, wherein said audio means includes a piezoelectric pager element.

12. A self-contained bandage according to claim 6, wherein said feedback means comprises only passive elements.