METHOD AND DEVICE FOR MONITORING A TREATMENT OF THE HUMAN OR ANIMAL BODY

Abstract

Process for monitoring a treatment on the human or animal body, in which, in the area of a nerve cord, current pulses of a specified pulse width are applied in the body and in the area of a muscle that is in communication with the nerve cord, voltage signals triggered by the current pulses are measured, in a preparatory step at least one criterion of voltage signals which are still measurable in response to current pulses being determined and during the treatment, the amplitude of the current pulses being adjusted in such a way that the voltage signals received in response thereto approximately satisfy the criterion.

Claims

1. Process for monitoring a treatment on the human or animal body, in which, in the area of a nerve cord, current pulses of a specified pulse width are applied in the body and, in the area of a muscle in communication with the nerve cord, voltage signals triggered by the current pulses are measured, characterized in that, in a preparatory step, at least one criterion of voltage signals still measurable in response to current pulses is determined and that during the treatment, the amplitude of the current pulses is adjusted in such a way that the voltage signals obtained in response thereto approximately satisfy the criterion.

2. Process according to claim 1, characterized in that a criterion represents a temporal development of the voltage signal.

3. Process according to claim 1, characterized in that the voltage signals are measured using a frequency which is greater than the frequency of the current pulses, in particular at least 10 times the current pulse frequency.

4. Process according to any of the preceding claims, characterized in that one criterion is a detection level of voltage signals that are still measurable in response to current pulses.

5. Process according to claim 4, characterized in that a first warning signal is triggered when the amplitude of the current pulse required for obtaining the detection level decreases to below a first specified threshold value.

6. Process according to claim 4 or claim 5, characterized in that a second warning signal is triggered when the amplitude of the current pulses required for obtaining the detection level decreases to below a second specified threshold value, the second specified threshold level being smaller than the first specified threshold level.

7. Process according to any of the preceding claims 4 to 6, characterized in that for obtaining the detection level, a mean of the voltage signals triggered by the current pulses and the average deviation of the voltage signals from the mean are determined, the detection level being determined as the level, at which the average deviation decreases to below a specified threshold value.

8. Process according to any of the preceding claims, characterized in that for obtaining the detection level, the spontaneous activity of the muscle without any stimulation by current pulses is measured and the detection level is set to a value exceeding the level of the spontaneous activity by a specified rate, preferably 30 V to 50 V.

9. Process according to any of the preceding claims 4 to 8, characterized in that the voltage signals are amplified using a carrier frequency amplifier, whose carrier frequency corresponds to the frequency of the current pulses.

10. Process according to any of the preceding claims, characterized in that the current pulses are applied using a surgical instrument, such as a scalpel, a cannula or the like.

11. Process, in particular according to any of the preceding claims, characterized in that a time interval between the application of the current pulses and the measurement of the voltage signals is set.

12. Process according to claim 11, characterized in that the voltage signals are only measured in a specified window of time after application of the current pulses.

13. Process, in particular according to any of the preceding claims, characterized in that, in a first pulse sequence of successive current pulses, a first current pulse with an amplitude having the first specified threshold value, a second current pulse with an amplitude having the second specified threshold value and a third current pulse with an amplitude exceeding the first threshold value are applied and a release signal is generated if none of the current pulses causes a voltage signal which is measurable in response thereto, the first pulse sequence being repeated when the release signal is to be generated.

14. Process according to any of the preceding claims, characterized in that, in a second pulse sequence, alternating, a first current pulse with an amplitude having the first specified threshold value and a second current pulse with an amplitude having the second specified threshold value are generated, the first warning signal being generated and the second pulse sequence being repeated, if only in response to the first current pulse a voltage signal is measurable.

15. Process according to any of the preceding claims, characterized in that a third pulse sequence is generated in response to the detection of a voltage signal as a reaction to a current pulse with an amplitude having the second threshold value, at which (amplitude), alternating, current pulses with different amplitudes, each situated below the second threshold value, being generated, a current pulse with an amplitude corresponding to the second threshold value being then generated again, when in response to no current pulse of the third pulse sequence a voltage signal is detected.

16. Device for implementing a process according to any of the preceding claims.

17. Device according to claim 16 having an arrangement for applying current pulses of a specified amplitude, frequency and pulse width in a human or animal body, an electrode arrangement for detecting voltage signals triggered by the current pulses, a device for determining criteria of the voltage signals, in particular of a detection level of voltage signals still detectable in response to the current pulses and a control device for adjusting the amplitude of the current pulses as a function of the voltage signals obtained in response thereto in such a way that the voltage signals approximately satisfy the criteria.

18. Device according to claim 17, characterized by a device for generating optical and/or acoustic warning signals when the regulated amplitude of the current pulses decreases to below a specified threshold value.

19. Device according to claim 17 or claim 18, characterized by a carrier frequency amplifier for amplifying the voltage signals, the carrier frequency being specified by the frequency of the current pulses.

20. Device according to any of the claims 17 to 19, characterized in that the arrangement for applying the current pulses has a surgical instrument equipped with an electrode arrangement, such as a scalpel, a cannula or the like.

21. Device according to any of the claims 16 to 20 having a voltage signal detection device, by means of which a measurement of voltage signals takes place only within a specified selectable window of time after application of the current signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 shows a schematic representation of a first current pulse sequence,

[0037] FIG. 2 shows a schematic representation of a second current pulse sequence, and

[0038] FIG. 3 shows a schematic representation of a third current pulse sequence.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0039] The first current pulse sequence, shown in FIG. 1, comprises a first current pulse having an amplitude of 6 mA corresponding to the second threshold value, a second current pulse having an amplitude of 10 mA corresponding to the first threshold value, a third current pulse having an amplitude of 11 mA, and three successive current pulses having an amplitude of 20 mA each. If none of these current pulses causes a voltage response, it may be safely assumed that the current pulse application is taking place at a sufficient distance from the monitored nerve path. Related thereto, a voltage response will only be accepted if a detection level is reached. In the embodiment of the invention, which is explained based on the drawing, the detection level is determined in that, in a preparatory step, the spontaneous activity of the muscle is first measured without any stimulation using current pulses and the detection level is set to a value exceeding the level of the spontaneous activity by 30 V to 50 V.

[0040] In the second current pulse sequence, shown in FIG. 2, alternating, a first current pulse having an amplitude corresponding to the first threshold value and a second current pulse having an amplitude corresponding to the second threshold value are generated. The first warning signal is triggered if a voltage response can only be detected when the first current pulse is applied.

[0041] The third current pulse sequence, shown in FIG. 3, is triggered when during the second current pulse sequence, shown in FIG. 2, a voltage response is also obtained in response to a current pulse having an amplitude corresponding to the second threshold value. Then, alternating, current pulses of 2 mA and 4 mA respectively are generated, each having an amplitude below the second threshold value. Only when no voltage signal can be detected in response to any of these pulses having an amplitude of 2 mA and 4 mA, a current pulse having an amplitude of 6 mA corresponding to the second threshold value will be applied again. If even in response to this current pulse no voltage signal can be detected, the application of current pulses according to the second current pulse sequence, illustrated in FIG. 2, takes place automatically. If no signal can be detected even in response to this current pulse sequence, the application of current pulses according to the first current pulse sequence takes place.