ELECTRICAL THERAPY APPARATUS WITH VARIABLE MODULATION FREQUENCY

Abstract: An electrical apparatus for use e.g. in treating a living system applies a modulation rf field to the system e.g. to produce therapy. The form of the modulation is varied with time. A portable apparatus is described for attachment to the skin of a patient to produce improved wound healing. The apparatus emits a carrier of e.g. 25.00 Mhz which is modulated at a frequency (MF1) for a first period (R1) and then at a frequency (MF2) for a second period (R2).

Description: ELECTRICAL THERAPY APPARATUS WITH VARIABLE MODULATION FREQUENCY DESCRIPTION This invention relates to an electrical therapy apparatus having a variable modulation frequency. It has been known for many years that improved healing rates can be achieved by applying RF electromagnetic fields to wounded tissue in such a manner as to produce tissue heating. This technique is known as diathermy. More recently it has been appreciated that the therapy produced by an applied RF field is not characterised solely in terms of tissue heating produced by the field. A discussion of this topic is given in "Healing by Electromagnetism - Fact or Fiction" New Scientist 22nd April 1976. In my published UK Application 2 027 594 there is described a portable low power apparatus for attachment to a patient to produce therapy with an electromagnetic field which does not produce any substantial tissue heating. The apparatus produces an electromagnetic field typically in the frequency range of 3-30 MHz; typically, a frequency of 25 MHz is selected. In my published EPC application A 0 132 051, a timing arrangement is disclosed for controlling the treatment periods of the therapy apparatus. The timer can operate to cause the field to be applied for a treatment period of for example one hour followed by a dwell period when no field is applied e.g. of one hour. The apparatus operates cyclicly. Whilst the RF field is being applied, it has been pulse modulated which has been found to improve the therapeutic effect. Typically, the continuous output of an oscillator (operating in the 3-30 MHz range) is modulated to produce RF pulses of 100 μ sec duration at intervals of 1 m sec. The arrangement operates to _2 produce a field of typically less than 100 μW cm as measured at the skin of the patient, i.e. at a field strength which does not produce any tissue heating. The reason for the improvement in therapy produced by the pulse modulation is not fully understood. It has now been found according to the invention that the nature of the pulsing surprisingly results in substantially different therapeutic effects and in accordance with this invention, it has been appreciated that if the rate of modulation is varied with time, substantially improved therapeutic results occur. Thus in accordance with the invention there is provided electrical apparatus for influencing a metabolic characteristic of a living system comprising means for applying a current to a living system to alter a metabolic characteristic thereof, the apparatus including modulator means for producing a current which is modulated during the time it is applied to said system, and characterised by means for changing with time the modulation effected by the modulator means. Preferably the apparatus includes an antenna for emitting said field, oscillator means for energising the antenna, and said modulator means is arranged to modulate the output of the oscillator means. - 4 - Preferably, the modulator means is arranged to modulate the oscillator output from an "on" state to an "off" state sequentially. Conveniently the modulator means includes a multivibrator for sequentially switching the oscillator on and off, the multivibrator having a selectively variable time period, and including sequencer means for selectively varying said time period in a predetermined sequence. Preferably said sequence is programmable. The invention has particular but not exclusive application to treating patients in the manner described in my published specifications aforesaid. Also, the invention has application to treating patients in bed by means of a coil arrangement installed in or adjacent to the bed. The invention also has application to systems other than human patients, for example animals or to treat cell cultures used in bio-engineering. In order that the invention may be more fully understood embodiments thereof will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a block schematic diagram of an apparatus according to the invention ; Figure 2 illustrates in more detail the circuit of the modulator shown in Figure 1; Figure 3 illustrates a portable apparatus according to the invention; Figure 4 illustrates various waveforms produced during operation of the device shown in Figures 2 and 3; Figure 5 illustrates an antenna coil arrangement for use in a hospital bed; Figure 6 illustrates a coil arrangement for use with a bioreactor vessel for cell cultures; and Figure 7 illustrates another version of the apparatus for use with cell cultures. Referring firstly to Figure 1, this shows the general configuration of apparatus according to the invention. An oscillator 1 is arranged to drive an antenna 2 which is arranged adjacent a patient to be treated. Conveniently, the antenna 2 comprises a flexible coil the inductance of which forms part of the frequency determining time circuit of the oscillator 1. Further details of such an arrangement are described in my US Patent No. 4 412 540. The oscillator typically operates in the range of 3-30 MHz and conveniently the selected operating frequency is 25 MHz. The output of the oscillator is modulated by a modulator 3 which provides a cyclic enabling signal to the oscillator 1 such that the oscillator only operates during the occurence of the enabling signal. The modulator 3 is shown in more detail in Figure 2 and consists of a 555 monostable multivibrator 4 which provides a cyclic enabling signal on line 5 for the oscillator 1. The period of the multivibrator 4 is controlled by means of variable resistance arrangements defined by resistor Rl and transistor TR1, and resistor R2 and transistor TR2 respectively. The resistance presented by the transistor TR1 and TR2 is controlled by a logic sequencer 6 that applies a time varying set of control potentials to the bases of the transistors on lines 7, 8. The sequence of resistance changes produced by sequencer 6 may be programmable by means of a programmer unit 9. The programmer 9 may take a number of different forms. It may comprise an arrangement on a chip for programming the sequencer 7 or may comprise a device for receiving a pre-coded magnetic card bearing program information, or may comprise for permitting downloading of data from a remote location e.g. down a telephone line. The transistor TR2 produces coarse changes in frequency whereas transistor TR1 produces fine changes. Thus in use, the multivibrator 4 produces initially a modulation at a first frequency for a predetermined time, followed by a modulation at a frequency for a second predetermined time. The sequencer 6 may control the multivibrator to produce further modulation frequencies for further predetermined times. At the end of the sequence, the sequencer may return to the first frequency so that the entire cycle can be repeated. The multivibrator 4 may have a fixed mark to space ratio (ratio of on to off time) or this itself may be programmable and varied in a predetermined time sequence (by means not shown) . The apparatus may be embodied in a portable battery driven apparatus as shown in Figure 3. The modulator and the circuitry of the oscillator 1 are contained in a flat circular housing 10, typically of 3 cm diameter. The antenna includes a radiating conductor, which in this example comprises a loop of coaxial cable. A battery (not shown) is also included within the housing 10. This portable device is, in use, attached to the skin of a patient such that the antenna overlies an area to be treated, and the antenna emits electro¬ magnetic radiation which in this example is used to produce an improved tissue healing rate e.g. for a wound or a sore. The field strength produced at the skin of the patient is typically less than 100 μWcm —2 i.e. such as not to produce any substantial tissue heating. The oscillator 1 produces a carrier frequency CF of typically 25.00 MHz as shown schematically in Figure 4(a). The modulator 3 produces a cyclic enabling signal for the oscillator 1 of frequency MF shown schematically in Figure 4(b) such that the output of the oscillator is modulated as shown in Figure 4(c). Two different modulating frequencies MF and MF,, having respective periods T and T are shown. The modulating frequency MF is produced for a period by R.. and the modulating frequency MF is thereafter produced for a period R . The specific values of MF and R are adjustable in a programmable sequence by means of the logic sequencer 6. The modulating frequency MF has a mark to space ratio of t, . : t, and the corresponding ratio for MF is _.A : t__.__>. The mark to space ratio for the multivibrator 4 may be programmable (by means not shown) to adjust the value of t A, : t_B, with time. The reason why the change in modulation frequency produces an improved result is not fully understood. It is possible that the different fundamental frequencies MF , MF etc used in the modulation process invoke different specific reasonances in a biological system. Alternatively or additionally, it may be that the improved result is provided due to the fact that the pulses of the modulation frequency MF produce a number of harmonics centered on MF and that the harmonics contribute to the therapeutic process. Whatever the reason, different biological systems produce different levels of response to different patterns of the frequency modulation, and appropriate patterns of modulation that produce an improved therapy can be determined by experiment. Various examples of different modulation frequency patterns will now be described: Example 1 The modulation frequency is applied as a series of values MF.. , MF- ... MF each with an equal period R.. , R 2 ... R of three minutes, each value of MF increasing from the previous value in equal steps of 50 Hz starting from a value of 15 Hz. Example 2 The modulation frequency is applied in a series of steps as in Example 1 but the periods R , R etc are made unequal e.g. three minutes for R. , six minutes for R, three minutes for R. six minutes for R_ etc, Example 3 The modulation frequency is stepped upwardly and downwardly in a programmed sequence as follows MF = 1000 Hz, MF = 1200 Hz, MF = 800 Hz, MF 4 = 400 Hz, MF 5 = 1600 Hz. The respective periods R. , R„ etc may be all equal or of different lengths. Example 4 The periods R_ , R_ etc are reduced from the long duration measured in minutes mentioned above, to periods comprising a packet of 2 or 3 cycles of the modulation frequency MF. , MF-. Example 5 The shape and/or mark to space ratio of the modulation frequency is altered for successive periods R , R ... R thereby altering the harmonic content for successive periods R. Clearly features of the above described examples may be used individually or in combination. For example the harmonic modification described in Example 5 could be used in Examples 2 or 3. An alternative embodiment comprises a mains driven apparatus for use with larger antenna configurations. For example, as shown in Figure 5, an arrangement of antenna coils may be embodied in a bed for treating a prone patient. A number of specially configured antenna coils 30 to 40, which may be operable individually or concurrently are driven by the oscillator 1 to produce treatement of various parts of the human body as annotated in the Figure. Alternatively, the coils may be driven individually at respective different frequencies. The resulting therapy has particular benefit to generalised systemic pathologies especially when the modulation frequency is varied as discussed with reference to Figure 4. Conveniently, the strength of the field produced by the coils as measured at the skin of the pati.ent, i.s less than 100 μ W cm-2 The invention also has application to processes other than therapeutic treatment, for example modifying growth or other characteristics of a cell culture for use in biotechnology. Referring to Figure 6, this shows a helical coil arrangement 41 that is connected as the antenna 2 * in the circuit arrangement of Figures 1 and 2, for treating a cell culture (not shown) in a bioreactor 42. Another similar arrangement is shown in Figure 7 in which the coils are arranged in concentric loops 43, 44, 45, 46, connected in parallel. The circuit arrangement of Figures 1 and 2 is arranged in a module 47, conveniently battery driven, arranged on the side of the bioreactor 42. The invention also has application to the control of the flow of material through a wall of a vessel, e.g. for the controlled release of a substance such as a drug in the manner desribed for example in my PCT Application No. GB85/00510. Whilst in the described embodiments, the modulation frequency is caused to change both in frequency and/or time in a predetermined sequence, it may be possible to use the response of tissue to the applied field to alter the modulation frequency. Thus, a sensor may be provided associated with the tissue or tissue culture, the sensor providing an indication of the response of the tissue to the applied field. The sensor could be used in a feed back circuit to control the modulation frequency in such a manner as to tend to improve the response of the tissue to the applied field. Moreover, whilst the antenna is described herein as my conventional inductive antenna 2 as disclosed in my applications aforesaid, the invention may have application to other systems which produce a current in a living system for example by means of a capacitive plates or a simple dc current injection system. Also, with the antenna arrangement 2 described previously, it may be advantageous in some circumstances to utilise a static or other field with a vector direction extending at right angles or some other direction to the vector direction of the field produced by the antenna 2.

Claims: CLAIMS 1. Electrical apparatus for influencing a metabolic characteristic of a living system comprising means for applying a current to a living system to alter a metabolic characteristic thereof, the apparatus including modulator means for producing a current which is modulated during the time it is applied to said system, and characterised by means for changing with time the modulation effected by the modulator means. 2. Apparatus according to claim 1 wherein said current applying means comprises means for applying a magnet and/or electric field to the system. 3. Apparatus according to claim 1 including an antenna for emitting said field, oscillator means for energising the antenna, and said modulator means is arranged to modulate the output of the oscillator means. 4. Apparatus according to claim 3 wherein the modulator means includes a multivibrator for sequentially switching the oscillator on and off, the multivibrator having a selectively variable time period, and sequencer means for selectively varying said time period in a predetermined sequence. 5. Apparatus according to claim 4 including programmer means for programming the sequencer means to operate in a programmed sequence. 6. Apparatus according to claim 3 ' including a portable body member containing said modulator and circuitry of said oscillator means, and flexible antenna means connected onto the body member. 7. Apparatus according to claim 6 adapted to overlie skin of a patient and adapted to produce a field strength when measured at the skin of less than 100 Wcm "2 . 8. Apparatus according to claim 3 wherein the antenna includes a plurality of antenna coils. - 18 - 9. Apparatus according to claim 8 wherein said coils operate concurrently at respective different frequencies. 10. Apparatus according to claim 8 wherein said coils are arranged in a bed for treating a patient. 11. Apparatus according to claim 3 including a vessel to receive a biomass and wherein the antenna is configured about the vessel for treatment of the biomass. 12. Apparatus according to claim 3 wherein said modulator means is operative at a first modulating frequency (MF ) for a first period of time (R. ) - and thereafter steps to operate at a second modulating frequency (MF,,) for a second period of time (R-) . 13. Apparatus according to claim 12 wherein the second modulating frequency (MF,,) is greater than the first modulating frequency (MF ) . 14. Apparatus according to claim 12 wherein the second modulating frequency (MF ) is less than the first modulating frequency (MF ) . 15. Apparatus according to claim 12 wherein the first and second periods (R. , R-) are of equal duration. 16. Apparatus according to claim 12 wherein the mark to space ratio of the modulation frequency is adjustable.

Inventors: BENTALL RICHARD HUGH CAMERON, BENTALL, RICHARD, HUGH, CAMERON
Applicants: BENTALL RICHARD HUGH CAMERON, BENTALL, RICHARD, HUGH, CAMERON
Application year: 1988
Main classification: A61N1
IPC codes: A61N1