DE3047402A1 - Electric stimulation therapy instrument - generates AC with asymmetrical waveform to reduce risk of electrode burns - Google Patents

Abstract

This electric stimulation therapy instrument for strengthening atrophied muscle etc. eliminates electrode burns by virtue of the special asymmetric wave form of the a.c. generated. The positive and negative wave envelopes enclose equal areas and the positive amplitude is equal to twice the negative one. Pulse bursts are variable in duration. Wave forms are produced from triangular oscillations by means of pulse shaping circuitry.

Description

Discussion:

Electrical stimulation therapy device for electrical stimulation.

The invention relates to a stimulation current therapy device of special 'biphasic' Pulse shape (Fig. 1), as one, two and multi-channel device with adjustable amplitude modulation (Duration and level) of the impulse, especially for functional electrical stimulation the muscles and the nerves.

With this stimulation current therapy device, a functional Electrostimulation e.g. performed the forearm extensor in patients with elemiplegia to strengthen the extensor innervation and to tighten the flexor spasm reduce; or secondly, in the case of atrophic muscles, the aim is to strengthen the muscles the stimulation can be achieved.

There are electrical stimulation therapy devices known which modulate the amplitude 'Menophasic' impulses triangular and / or rectangular in shape. These Devices are constant current = c.c.

mostly in Europe, or constant voltage = c.v., in North America. It was published in 1974 by Peter Suhel in a monograph of the medical faculty the University of Lublijana (Juguslavia) proposed a biphasic voltage pulse.

With these pulses, on the one hand, the galvanic load ( except for the impulse proposed by P. Suhel) to limit the stimulation time to about 15 minutes depending on the current strength.

From an electrical point of view, human tissue is a resistor-capacitor network (Fig. 7), the sharp changes in current or voltage lead to highly sensitive ones Nuisance caused by charging and discharging currents of the fabric capacitors. This will For example, in patients with hemiplegia, the burning of the electrodes sometimes causes the spasm increased instead of decreased as desired and with the stimulation of the atrophic muscles the force of contraction is generated by the burning of the electrodes and not by the tension the muscles are limited.

The object of the invention was to make these side effects clear to reduce and to make the therapy safer, since careless operating personnel Chemical burns are possible under the electrodes.

This object is achieved according to the invention in that a current pulse of a special 'biphasic' form is generated by a pulse generator. This Pulse with a positive pulse component and a negative one fulfills the condition: JJ + .dt dt + in + JJ # .dt = 0 (Fig 1).

The pulse generator consists of a triangular pulse generator with a following Pulse shaper stage. This is separated by an R-C-L combination at the entrance and two adjustable Output amplifiers for the plus and minus components of the impulse, which can change the transmission behavior at different Impulse waves (T1) can be linearized.

To take full advantage of this 'biphasic' pulse the envelope of the Tiplitude modulation of each channel (1 up to several) matched to a trapezoid with the same rise and fall time (Fig 3), as has been shown to be useful in stimulating patients prone to spasms with conventional devices often unwanted reflexes are triggered by the too rapid decay of the amplitude envelope.

Depending on the resilience of the muscle being treated, this should also be the case The ratio of the duration of the swelling (T1Sch) to the swelling pause can be variable. This was solved by a readjustment for T1Schw = 1/4 to about 3/4 of the threshold period (Fig 3).

In the case of two-channel devices, it is important that the threshold periods overlap can be readjusted for both channels, since each patient has a different stimulus threshold has (Fig 4). Thus, for example, an alternating S6reCkell ZlZ des Through the stimulation of the muscles of the anterior thigh through one canal and the muscles of the thigh joint through the second Channel can be achieved, with multi-channel devices can be set through the different Dead times of the swell periods of the various channels are a complex movement process can be mimicked, as the channels are just as adjustable as a well-tuned one Requires movement (Fig 5).

The advantages that can be achieved with the invention are particular in the fact that the possible muscle tension is significantly higher than that with conventional ones Comparison devices achievable with the same subjective annoyance of the patient (Our own study on 6 massage students - average age approx. 20 years - resulted in an average increased tension with the same subjective annoyance of about 43% when stimulating the quatriceps femoris muscle. Own still unpublished Experiment from May 10th, 1981), i.e. with the same tension is the subjective annoyance lower and thus also the excitation of distant reflexes, which can be seen as a side effect.

Therapy safety is significantly increased by the elimination of the galvanic exposure of the skin.

When stimulating atrophic muscles, there is no electrode burning the limit of the applicable peak current strength but the possible muscle tension.

The conditions are clearer, since the charging and discharging currents an equivalent circuit built by the applicant (Fig 7 and 8) in the new special A biphasic 'pulse are significantly lower than with the triangular or square pulses conventional electrical stimulation therapy devices.

An exemplary embodiment is shown in Fig. 9 as a two-channel device.

Fig 1 Pulse shape of the special 'biphasic' pulse Fig 2 Circuit of the pulse generator with pulse shaper Fig 3 Envelope of the amplitude modulation - general-Fig 4 Envelope of the amplitude modulation with 2 channels Fig 5 Envelope the amplitude modulation with several channels Fig 6 Circuit of the output stage Fig 7 Circuit for determining the electrical parameters of human tissue Fig 8 Equivalent circuit of human tissue and derivation in various Impulse Fig 9 Block diagram of a completed 2-channel device Fig 10 Circuit of the clock generator for the threshold time Fig 11 Circuit of the needle pulse generator for Control of the @@@@@@ curve former Fig 12 Switching of the @@@ curve former Fig 13 Circuit of the multiplier for amplitude modulation of the special 'biphasic' Impulse Blank page

Claims (3)

Claims: 1) Stimulation current therapy device special ~ biphasic ' Pulse shape, as a single two- and multi-channel device with adjustable amplitude modulation (Duration and level) of the impulse, especially for functional electrical stimulation the muscles and the nerves, characterized in that the pulse generator (pulse duration and pause adjustable) special 'biphasic' pulses are generated, where # J + .dt + # J-.dt = 0 (Fig. 1 and 2). The pulses are generated from triangular pulses in the pulse shaper. This is characterized by an R-C-L combination at the entrance and two separately adjustable output amplifiers for the plus and minus part of the pulse. 2) i # Adjustable amplitude modulation of the special ~ biphasic Impulse for one-, two- and multi-channel devices, marked by this: a) with single-channel devices: that the envelope of the amplitude modulation is a trapezoid with the same rise and fall time, whereby this is about 1/4 of the adjustable threshold period (TSchw = 4 - 40sed, the threshold duration (T1sc be is in the middle of the threshold duration adjuster about 1/2 of the duration of the threshold period and can be readjusted in the range from about 1/4 to 3/4 Swell period (Fig 3). b) for two-channel devices: that two separately adjustable (height, Threshold duration) channels, the amplitude modulation described before (single-channel device) is output, the two channels working offset by 1/2 the threshold period. (Fig 4) c) for multi-channel devices: that two channels (as described above) as pilot channels work for every i further channels (@@@@@@@@@@@@ i = 1 to n) #, whereby the dead time, the duration of the threshold and the amplitude level can be set individually for each additional channel is (Fig 5). 3) Output amplifier for the special 'biphasic' pulses, respectively for a channel of the devices described before, characterized in: that the plus portion and the minus part of the pulse is amplified separately, both amplifier parts are individually adjustable in the gain to the condition JJ + .dt + ~ dt = 0 exactly Via output transformer from the low-voltage part of the circuit to the patient circuit transferred to. (Fig 6) 1) .... main claim 2) .... and 3) .... subclaims.