TREATMENT BED

Abstract

The invention relates to a treatment bed for supporting patients in a sitting and/or lying manner for the duration of a treatment and/or diagnosis. The treatment bed has a support surface which consists of one or more segments and on which the patient is supported during the treatment and/or diagnosis. Multiple capacitive measuring electrodes for the contactless capacitive detection of EKG signals of a patient supported on the support surface are arranged in at least one segment of the support surface on the surface side closer to the patient. The treatment bed further has at least one electronic signal processing system which is connected to the measuring electrodes and is designed to process signals, in particular to amplify signals, of the electric signals of the measuring electrodes. In addition to the measuring electrodes, the treatment bed also has at least one injection electrode which is designed to teed injection signals into one or more of the measuring electrodes via the patient supported on the support surface. The electronic signal processing system is additionally designed to determine the quality of the capacitive coupling of one or more or all of the measuring electrodes to the patient by means of the signals received via the measuring electrodes using the signal components which are contained in the signals and originate from the injection signals.

Claims

1. A treatment couch for supporting patients in a sitting and/or lying position for a treatment and/or diagnosis, comprising: a supporting surface comprised of one or more segments and on which the patient is supported during the treatment and/or diagnosis, multiple capacitive measuring electrodes for the contactless capacitive detection of ECG signals of a patient supported on the supporting surface arranged in at least one segment of the one or more segments of the supporting surface, wherein the multiple capacitive measuring electrodes are on a side of the supporting surface that is near the patient, at least one electronic signal processing system connected to the measuring electrodes for processing the electrical signals of the measuring electrodes, at least one injection electrode for feeding injection signals into one or more of the measuring electrodes via the patient supported on the supporting surface, wherein the electronic signal processing system is designed to determine from the signals received by way of the measuring electrodes, on a basis of signal components that are contained therein and originate from the injection signals, a quality of capacitive coupling of one or more or all of the measuring electrodes to the patient.

2. The treatment couch as claimed in claim 1 wherein one or more or all of the measuring electrodes and/or a first and/or a second injection electrode is/are formed as textile capacitive electrodes which are embedded in a structure near a surface of the side of the supporting surface near the patient.

3. The treatment couch as claimed in claim 1 wherein the electronic signal processing system is arranged on the treatment couch away from the measuring electrodes and/or the injection electrodes.

4. The treatment couch as claimed in claim 1, further comprising: an electrical terminal connector for electrically coupling a treatment monitor to the treatment couch and its at least one electronic signal processing system, wherein the at least one electronic signal processing system is designed to emit on a basis of the signals of the measuring electrodes ECG signals of the patient in a normalized form by way of the electrical terminal connector.

5. The treatment couch as claimed in claim 1, further comprising at least one electric motor, and wherein at least one segment of the one or more segments is adjustable arbitrarily into different positions by the at least one electric motor.

6. The treatment couch as claimed in claim 1, further comprising at least one electric motor, and wherein the treatment couch is adjustable from a sitting position into a lying position and vice versa by the at least one electric motor.

7. The treatment couch as claimed in claim 1 further comprising multiple fixable rollers for supporting the treatment couch with respect to a floor.

8. The treatment couch as claimed in claim 1, further comprising at least one arm rest, wherein the at least one arm rest is secured to or securable to either a left or right of the supporting.

9. The treatment couch as claimed in claim 1 wherein the at least one electronic signal processing system is designed for determining the quality of the capacitive coupling of a measuring electrode of the multiple capacity measuring electrodes on the basis of amplitude values and phase positions of signal components of the injection signals that are received by way of the measuring electrode.

10. The treatment couch as claimed in claim 1 wherein the at least one electronic signal processing system is designed for determining the heart rate or a variable derived therefrom of the patient supported on the supporting surface.

11. The treatment couch as claimed in claim 1 further comprising at least one acoustic and/or optical signal transmitter, wherein the at least one electronic signal processing system is designed to activate the at least one acoustic and/or optical signal transmitter to issue an alarm signal when there are predetermined signal combinations of detected ECG signals and the quality of the capacitive coupling.

12. The treatment couch as claimed in claim 1 wherein the at least one injection electrode comprises a first injection electrode and a second injection electrode, and wherein the injection signals comprise a first injection signal and a second injection signal, wherein the second injection signal is different from the first injection signal, wherein the at least one electronic signal processing system is cojnfigured such that the first injection signal is fed into the first injection electrode from the at least one electronic signal processing system and, overlapping in time or at the same time, the second injection signal is fed into the second injection electrode from the at least one electronic signal processing system.

13. The treatment couch as claimed in claim 1 wherein one or more or all of the at least one injection electrodes is/are formed as a capacitive and/or galvanic electrode.

Description

[0040] The invention is explained in more detail below on the basis of exemplary embodiments with the use of drawings, in which:

[0041] FIG. 1 shows a treatment couch in a perspective representation and

[0042] FIG. 2 shows the multi-layered structure of a textile electrode and

[0043] FIG. 3 shows the treatment couch according to FIG. 1 with regard to the electrical signal flows and

[0044] FIG. 4 shows a signal detecting circuit of a measuring electrode and

[0045] FIG. 5 shows an equivalent circuit diagram of a 2-channel system and

[0046] FIG. 6 shows an equivalent circuit diagram of the injection electrodes

[0047] In the figures, the same designations are used for elements that correspond to one another.

[0048] The treatment couch 9 shown in FIG. 1 has a supporting surface 3, 4, 6, which in this case is divided into three segments. The supporting surface has a back segment 3, serving as a back rest, a seat segment 4 and a foot segment 6, serving as a foot rest. The segments 3, 4, 6 of the supporting surface are in each case padded, wherein the padding material is covered with a covering material Integrated in the covering material or directly under the covering material are multiple electrodes 30, 30, 41. These electrodes 30, 40, 41 are not actually visible from the outside, but in FIG. 1 are depicted as visible elements to illustrate the invention. The electrodes 30, 40, 41 take the form of six capacitive measuring electrodes 30 and also a first capacitive injection electrode 40 and a second capacitive injection electrode 41. It is possible for example, as shown in FIG. 1, for four measuring electrodes 30 to be arranged in the back segment 3 and two measuring electrodes 30 to be arranged in the seat segment 4. Moreover, the first and second injection electrodes 40, 41 are likewise arranged in the seat element 4.

[0049] The treatment couch 9 has a subframe 90, which bears the supporting surface 3, 4, 6. The subframe 90 is supported on the floor by way of four rollers 91, which are fixable. By way of electric motors 92 arranged on the subframe 90 or in the vicinity of the segments 3, 4, 6, at least some of the segments, for example the back segment 3 and foot segment 6, can be adjusted electromotively into various positions.

[0050] The measuring electrodes 30 and the injection electrodes 40, 41 are electrically connected to an electronic signal processing system 1, arranged for example in the subframe 90. The electronic signal processing system 1 detects the signals of the capacitive measuring electrodes 30 and, to detect the quality of the capacitive coupling of the measuring electrodes 30 to the patient, also injects injection signals by way of the injection electrodes 40, 41 into the patient. The electronic signal processing system 1 may also be designed to process the recorded ECG signals in a normalized form and to emit them to the outside by way of a terminal connector 93, for example in the form of an electrical plug-in connector. Accordingly, a treatment monitor may be coupled to the terminal connector 93, in order to visually present the emitted normalized ECG signals and possibly document them.

[0051] The electronic signal processing system 1 may also be designed for monitoring the ECG signals in combination with the quality of the capacitive coupling of the measuring electrodes 30 to the patient for critical signal combinations. When a critical signal combination is detected, the electronic signal processing system 1 may activate a signal transmitter 94, in order to draw attention to the critical state.

[0052] The treatment couch 9 may furthermore have a left arm rest 36 and a right arm rest 35, also a head-rest element, arranged on the back segment 3, and a foot-resting surface 60, arranged on the foot segment 6.

[0053] FIG. 2 shows by way of example a textile electrode 1, as can be used as a measuring electrode 30 or else an injection electrode 40, 41.

[0054] FIG. 2 shows the textile electrode 1 with the individual layers in an isometric view before the layers are adhesively bonded together. Three electrically conductive layers 61, 62, 63 of an electrically conductive textile material and three insulating layers 64, 65, 66 of an insulating textile material can be seen. The uppermost electrically conductive layer 61 is the sensor layer of the electrode, which serves for the capacitive incoupling of the signal to be measured by means of the electrode. The middle electrically conductive layer 62 is a guard layer, which serves for shielding the sensor layer 61 from external interfering influences, in particular ESD influences. The lower electrically conductive layer 63 is a reference potential layer, which is to be connected to a reference potential. The sensor layer 61 has at a corner a clearance 67, through which a contact link 68 for the electrical contacting of the sensor layer 61 is formed. The guard layer 62 has a contact link 69, which is formed by pieces of textile material of the guard layer 62 to the left and right of the contact link 69 having been cut away. The contact link 69 serves for the electrical contacting of the guard layer 62. The reference potential layer 63 is formed in a way comparable to the sensor layer 61, but with a contact link 70 on the opposite side. The contact link 70 is formed as the result of a clearance 71, which is cut out from the textile material of the reference potential layer 63. The uppermost insulating layer 64 has at a corner a clearance 72, which lies underneath the contact link 68. The middle insulating layer 65 has at an opposite corner of the same side a clearance 73. The clearance 73 overlaps with the contact link 70. The lowermost insulating layer 66 does not have such clearances. The layers 61-66 may be brought into the outer contour described and shown for example by laser cutting.

[0055] The outer form of the electrode 1 or the individual layers 61-66 does not necessarily have to be substantially rectangular, as represented in FIG. 2, but may assume any other desired form, such as for example oval, rectangular with rounded corners or circular.

[0056] An electronic signal-amplification component 83, which serves for amplifying the electrical signals emitted by the capacitive textile electrode 1, is arranged in the vicinity of the textile electrode 1 shown in FIG. 2.

[0057] In this way, the treatment couch 9 with the technical elements explained represents a system for the capacitive detection of electrical biosignals from a biosignal source 2, i.e. from a patient. The function of such a system is explained in more detail below on the basis of FIGS. 3 to 6.

[0058] The system shown in FIG. 3 serves for the capacitive detection of electrical biosignals from a biosignal source 2, for example a human. For this, the treatment couch 9 is fitted with the corresponding capacitive measuring electrodes 30 and injection electrodes 40, 41. The injection electrodes 40, 41 are connected by way of separate electrical lines to devices 43, 44, which in FIG. 1 are only shown singly, but are provided separately for each injection electrode. The device 43 is a lowpass filter, for example with a cut-off frequency of 4 kHz. The device 44 is formed as a digital/analog converter, which converts a digital signal supplied by a central unit of the electronic signal processing system 1 into an analog voltage value and outputs it via the lowpass filter 43 to the respective injection electrode 40, 41.

[0059] The measuring electrodes 30 are connected by way of respective signal amplifiers 31, which may also be integrated in the respective textile electrode, to further signal processing means 33, 34. The measuring electrodes 30 or their signal amplifiers 31 may be connected in each case via an individual, separate signal path by way of signal processing means 33, 34 to the electronic signal processing system 1 or, if the complexity of the circuitry is to be reduced, be switched by way of a multiplexer 32 in each case to the same signal processing means 33, 34. The signal processing means 33 may be formed as a lowpass filter, for example with a cut-off frequency of 4 kHz. The signal processing means 34 may be formed as an analog/digital converter.

[0060] The respective analog/digital conversion or digital/analog conversion allows the signal processing to be performed completely digitally in the electronic signal processing system 1, with the advantage that signal processing algorithms of a relatively favorable complexity can be provided.

[0061] The electronic signal processing system 1 connected to the analog/digital converter 34 or the digital/analog converters 44 has the following structure. The digitized signals of the measuring electrode 30 that are detected by way of the analog/digital converter 34 are supplied to three different evaluation paths in the electronic signal processing system 1, to be precise one path for the evaluation of the signal components originating from the injection signals, one path for the ascertainment of the actual useful signals, to be specific the biosignals of the biosignal source, and one path that serves for common-mode rejection. First, the path for the evaluation of the signal components originating from the injection signals will be discussed. For this, first there is a buffer 10, in that the incoming data are first buffered in blocks, for example with a block size of 728 measured values. The block size is in this case chosen in particular such that full periods of the first and second injection signals are respectively stored in one block.

[0062] In a block 11, the signal components are filtered by a bandpass filter, for example by a non-rectangular window function, for example a Hanning filter. In a subsequent digital filter 12, a further filtering is performed, for example by means of a Fast Fourier Transform (FFT) or a Goertzel algorithm. The Goertzel algorithm allows the efficient determination of selected frequency components. With the data determined in this way, the quality of the capacitive coupling of the measuring electrode to the biosignal source, for example in the form of the coupling capacitance, can be determined in a block 15. The results of the quality determination can be output for example on a display device, for example a screen 5, or passed on for further processing.

[0063] By way of the filter block 14 shown approximately in the middle of the electronic signal processing system 1 in FIG. 1, the ECG signals are filtered out from the supplied signals of the measuring electrode. This may be performed for example by a two-stage FIR filter.

[0064] For the common-mode rejection, it is envisaged first to summate the supplied, digitized measuring signal by way of a summator 16. In this way, the common-mode signal is obtained. In a multiplier 17, the previously determined common-mode signal can also be amplified by a gain factor 18, for example in the range from 0 to 40 dB. The signal thereby formed is subsequently supplied to a further filter 19. The signal generated from the filter 19 is supplied on the one hand to the filter block 14, on the other hand to two summators 20.

[0065] In the blocks shown at the bottom in the electronic signal processing system 1, the first and second injection signals are generated in two signal generators 21, 22. The first injection signal may for example have a frequency of 1120 Hz at an amplitude of 100 mV, the second injection signal a frequency of 1040 Hz at an amplitude of 12.5 mV. Thus, the first signal generator 21 may be formed so as to directly emit an overlay of the first and second injection signals, while the other signal generator 22 only emits the first injection signal. In the summators 20, the signal emitted by the filter 19 is mixed with the respective injection signals to provide the common-mode rejection. The corresponding signals, which until then have been in a digital form, are converted by way of the already mentioned digital/analog converter 44 into analog signals and fed separately from one another via the filters 43 into the injection electrodes 40, 41.

[0066] For the dimensioning of the injection signals, a compromise has been found, allowing the injection signals to be placed at frequencies that are as close together as possible and offer a good demodulation rate, and at the same time allowing a sampling rates achievable for suitable precision analog/digital converters and available microcontrollers. Furthermore, the injection frequencies must be high enough to allow them to be sufficiently suppressed with respect to the useful signal (the ECG signal) by a single lowpass filter. As a result of this, a delimitation from movement artifacts, which lie in the range below 20 Hz, is also possible.

[0067] The amplitude of the injection signals also represents a compromise between a good signal-to-noise ratio and the lowest possible order of the lowpass filters, to allow simple signal processing.

[0068] FIG. 4 shows on the left by way of example a measuring electrode with the previously described multi-layered structure, which is arranged behind the textile surface 60 of the back segment 3. The reference potential layer 63 is connected to the system ground by way of a resistor 64. The sensor layer 61 is connected by way of a line first via an amplifier, for example an operational amplifier 65, to the guard layer 62. Furthermore, for detecting the already explained signals to be detected by way of the measuring electrode, the sensor layer 61 is connected to a measuring terminal 68, at which there is the measuring signal that is to be detected by means of the signal evaluation means 33, 34. To be able in addition to carry out a current measurement with respect to the injection electrodes 40, 41, a measuring resistor in the form of a shunt 66 is present on the line from the sensor layer 61 to the measuring terminal 68. The voltage dropping across the shunt 66, which is an indicator of the current flowing through it, is amplified by way of an amplifier 67 and delivered to an output terminal 69. The signal available at the output terminal 69 is supplied, possibly after prior filtering, likewise by way of analog/digital converters to the electronic signal processing system 1 and is further processed there.

[0069] The determination of the quality of the capacitive coupling, for example in the form of a coupling impedance, can be performed as follows. This is based on the equivalent circuit diagram shown in FIG. 5 and the electrical variables indicated there.

[0070] In FIG. 5, the equivalent circuit diagram of a 2-channel system (two measuring electrodes) with DRL signal injection is shown. In addition, here the parasitic impedance Z.sub.stray is taken into account. It is produced by the stray capacitances between the biosignal source and objects of the outside world and also between the measuring system and the outside world. This is particularly considerable in the case of a non-insulated power supply to the measuring system from the grid. U.sub.p represents the voltage signal present at the biosignal source with respect to the system ground. The following applies for the coupling impedance of an electrode:

[00001]$\begin{array}{cc}{\underset{\_}{U}}_{\mathrm{out}}={\underset{\_}{U}}_p.Math.\frac{{\underset{\_}{Z}}_{\mathrm{in}}}{{\underset{\_}{Z}}_{\mathrm{in}}+{\underset{\_}{Z}}_c}& \left(3.11\right)\\ {\underset{\_}{Z}}_c={\underset{\_}{Z}}_{\mathrm{in}}\left(\frac{{\underset{\_}{U}}_p}{{\underset{\_}{U}}_{\mathrm{out}}}-1\right)& \left(3.12\right)\end{array}$

[0071] Depending on the angular frequency w of the injection signal, the capacitance and the resistance can be determined from this:

[00002]$\begin{array}{cc}{C}_C=\frac{.Math..Math.\left({\underset{\_}{Y}}_c\right)}{}=\frac{.Math..Math.\left(\frac{1}{{\underset{\_}{Z}}_c}\right)}{}& \left(3.13\right)\\ \text{?}& \left(3.14\right)\\ R_c=\frac{1}{.Math.\left({\underset{\_}{Y}}_c\right)}=\frac{1}{.Math.\left(\frac{1}{{\underset{\_}{Z}}_c}\right)}.Math..Math.\text{?}.Math.\text{indicates text missing or illegible when filed}& \left(3.15\right)\end{array}$

[0072] The model shows however that the voltage U.sub.p is influenced by the impedances Z.sub.stray, Z.sub.drl and Z.sub.ci. It cannot be uniquely determined with the available measuring data.

[0073] To be able to determine U.sub.p, at least one further injecting electrode is required.

[0074] For this purpose, the DRL electrode may be divided into two separate surface areas. As a difference from dividing the measuring electrodes, this does not entail any disadvantage for the signal quality, because in the case of the DRL electrode it is only necessary to maximize the overall capacitance of the two areas. The corresponding equivalent circuit diagram can be seen in FIG. 6; the electrode capacitances and stray capacitances are in this case combined to form the impedance Z.sub.p. Two injection signals are fed in: Uinj2 with the angular frequency 2 over both areas and U.sub.inj1 with the angular frequency .sub.1 only over the first area. The two parts of the electrode respectively contain a shunt Z.sub.s1 and Z.sub.s2. Measuring the voltage at the shunts allows the complex current intensities I.sub.S1 and I.sub.s2 for the two angular frequencies .sub.1 and w.sub.2 to be determined. The shunts should be chosen to be resistive: because the injection signals lie above the ECG bandwidth, the predominantly capacitive coupling impedances Z.sub.drli, .sub.i are smaller with respect to the injection signal than with respect to the ECG signal. The resistive impedances of the shunts remain unchanged however. Consequently, they only produce a small voltage drop in the frequency band of the ECG signal, and consequently do not reduce the effectiveness of the DRL electrode, while the voltage drop in the band of the injection signals becomes greater, and consequently allows a more precise determination of I.sub.s. In addition, the model has the input impedances Z,.sub.in1 and Z.sub.in2, which model the corresponding parasitic properties of the amplifiers used for the shunt voltage measurement.

[0075] It is now intended to show that, with the voltages measured at the shunts, U.sub.s1,.sub.2 and U.sub.s2,1 and also U.sub.s1,2 and U.sub.s2, .sub.2, the voltage at the patient U.sub.p, .sub.2 and also the two coupling capacitances Z.sub.drl1, .sub.2 Z.sub.drl2, .sub.2 of the DRL electrode can be determined. The method by which the frequency components .sub.1 and .sub.2 belonging to the respective injection signals U.sub.inj1 and U.sub.inj2 can be demodulated from the measuring signal has already been described above. In the determination of the voltages and currents with the index .sub.1, the voltage source U.sub.inj2 is assumed as a short circuit, with the index .sub.2-U.sub.inj1. To simplify matters, instead of the impedances, the corresponding admittances may be used hereafter. First, the complex current intensities are to be determined by way of the coupling impedances. Kirchhoff's first rule gives:

I.sub.drl1,1=Y.sub.s1,1U.sub.s1,1=(U.sub.inj,U.sub.s1,1)Y.sub.inj,for i=1,2 (3.16)

I.sub.drl2,1=U.sub.s2,1(Y.sub.inj,1+Y.sub.s2,1) (3.17)

I.sub.drl2,2=Y.sub.s2,2U.sub.s2,2(U.sub.inj2U.sub.s2,2)Y.sub.in2,2 (3.18)

[0076] To simplify the further calculation, from here on two assumptions are made: [0077] the two shunts are of such a low resistance in comparison with the coupling impedances that U.sub.injU.sub.s applies to both electrodes and frequencies. U.sub.s are ignored from now on. [0078] the angular frequencies .sub.1 and .sub.2 are so close together that Y.sub.1Y.sub.2 applies to all of the admittances. It is assumed from here on that the admittances are frequency-independent.

[0079] Kirchhoff's second rule gives:

[00003]$\begin{array}{cc}\text{?}& \left(3.19\right)\\ \text{?}& \left(3.20\right)\\ \text{?}.Math..Math.0={\underset{\_}{U}}_{{\mathrm{drl}}_2,{}_2}-{\underset{\_}{U}}_{{\mathrm{drl}}_1,{}_2}=\frac{{\underset{\_}{I}}_{{\mathrm{drl}}_2,{}_2}}{{\underset{\_}{Y}}_{{\mathrm{drl}}_2}}-\frac{{\underset{\_}{I}}_{{\mathrm{drl}}_1,{}_2}}{{\underset{\_}{Y}}_{{\mathrm{drl}}_1}}.Math..Math..Math.{\underset{\_}{Y}}_{{\mathrm{drl}}_2}={\underset{\_}{Y}}_{{\mathrm{drl}}_1}.Math.\frac{{\underset{\_}{I}}_{{\mathrm{drl}}_2,{}_2}}{{\underset{\_}{I}}_{{\mathrm{drl}}_1,{}_2}}.Math..Math.0=-{\underset{\_}{U}}_{{\mathrm{inj}}_1}+{\underset{\_}{U}}_{{\mathrm{drl}}_1,{}_1}-{\underset{\_}{U}}_{{\mathrm{drl}}_2,{}_1}=-{\underset{\_}{U}}_{{\mathrm{inj}}_1}+\frac{{\underset{\_}{I}}_{{\mathrm{drl}}_1,{}_1}}{{\underset{\_}{Y}}_{{\mathrm{drl}}_1}}-\frac{{\underset{\_}{I}}_{{\mathrm{drl}}_2,{}_1}}{{\underset{\_}{Y}}_{{\mathrm{drl}}_2}}.Math..Math.\text{?}.Math.\text{indicates text missing or illegible when filed}& \left(3.21\right)\end{array}$

[0080] Entering 3.20 into 3.21 and converting produces:

[00004]$\begin{array}{cc}{\underset{\_}{Y}}_{{\mathrm{drl}}_1}=\frac{1}{{\underset{\_}{U}}_{{\mathrm{inj}}_1}}.Math.\left({\underset{\_}{I}}_{{\mathrm{drl}}_1,{}_1}-\frac{{\underset{\_}{I}}_{{\mathrm{drl}}_2,{}_1}.Math.{\underset{\_}{I}}_{{\mathrm{drl}}_1,{}_2}}{{\underset{\_}{I}}_{{\mathrm{drl}}_2,{}_2}}\right)& \left(3.22\right)\end{array}$

[0081] The following applies for the voltage U.sub.p:

[00005]$\begin{array}{cc}{\underset{\_}{U}}_{p,{}_2}={\underset{\_}{U}}_{{\mathrm{inj}}_2}-\frac{{\underset{\_}{I}}_{{\mathrm{drl}}_1,{}_2}}{{\underset{\_}{Y}}_{{\mathrm{drl}}_1}}=\frac{{\underset{\_}{I}}_{{\mathrm{drl}}_2,{}_2}}{{\underset{\_}{Y}}_{{\mathrm{drl}}_2}}& \left(3.23\right)\end{array}$

[0082] Consequently, the two coupling impedances of the DRL electrode can be determined from 3.22 and 3.20 and the component of the injection signal at the biosignal source can be determined from 3.23.