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WIRELESS MEDICAL DIAGNOSIS AND
MONITORING EQUIPMENT
This application is a continuation of application Ser. No. 09/822,152, filed Jun. 15, 2001, now U.S. Pat. No. 6,577,893 5 which is a continuation of application Ser. No. 09/379,763, filed Aug. 24, 1999, now U.S. Pat. No. 6,289,238 which is a continuation of Ser. No. 08/985,673 filed Dec. 5, 1997, now U.S. Pat. No. 5,957,854 which is a continuation of Ser. No. 08/605,197, filed Mar. 1, 1996, now U.S. Pat. No. 10 5,862,803 which is a national phase of international application PCT/EP95/02926, filed Sep. 2, 1994, (pending), which is hereby incorporated by reference herein.
BACKGROUND 15
The invention relates to a medical measured-data acquisition equipment for monitoring and diagnosis, in particular to EEG and EKG equipment, as well as to facilities for controlling the breathing, the 02 saturation content in the 20 blood, the body temperature, and for recording electric potentials or electrodermal activities such as the SSR (sympathetic skin response). Such monitoring and diagnostic equipment is used mainly in intensive-care stations in hospitals, or in the examination of patients. 25
Monitoring equipment is used also for monitoring infants at home, among other things. In the Federal Republic of Germany about 2000 infants die annually from the sudden infant death syndrome, a phenomenon, the causes of which have not yet been elucidated in spite of intensive research. 30 However, everything speaks for the fact that the sudden infant death is to be attributed to a failure of the respiratory function (apnea), and possibly of the cardiac function. It exclusively occurs during sleeping. The only preventive measure for preventing the sudden infant death currently 35 consists in the monitoring of the respiratory or cardiac function. Said procedure is useful in that by stimulating the infant immediately following failure of the respiratory function, the respiratory activity automatically starts again, with a few exceptions. 40
EKG and EEG facilities assume a special position among monitoring and diagnostic devices because their high medical conclusiveness. An electrocardiogram (EKG) is the recording of the time curve of heart action potentials; an electroencephalogram (EEG) is the graphic record of the 45 brain action potentials. The analysis of the EKG's and EEG's supplies important information about the heart or brain function of the patient.
Conventional monitoring and diagnostic equipment is structured in such a way that one or several electrode(s) 50 is/are mounted on the patient, which tap the respective signals (predominantly potential and impedance values) and transmit such signals via cables to amplifier units. Normally, separate electrodes are used for each measurement parameter. 55
Especially in EKG and EEG examinations, many cables are suspended on the patient, connecting the EKG/EEGelectrodes with the evaluator units, which process and record the signals. Such cables obstruct the patient and highly limit his or her freedom of movement, and, therefore, are only 60 conditionally suitable especially for carrying out examinations at stress (e.g. EKG's at stress). In addition, due to the stiffness of the cables and the lever forces connected therewith, the cables become easily detached particularly when the patient moves. Furthermore, in connection with infants, 65 there is the risk that they may play with the cables and detach the glued-on electrodes.
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The electrode cables are especially troublesome in connection with home or hospital monitoring of infants. The removal and reattachment of the electrodes is troublesome especially when garments are changed frequently (e.g. during the changing of diapers).
Furthermore, in complicated examinations with a great number of measured quantities such as, for example, in the polysomnography in connection with infants, problems arise on account of the fact that many relatively large electrodes have to be attached to the patient. Moreover, it is necessary in this connection to take into account the psychic stress of the patient, who is connected to an electrical device via a great number of cables. Such psychic stress may have a bearing on both the physical stressability and the physiological characteristic lines.
The above-described methods are high in expenditure, user-unfriendly, and under certain circumstances may require certain medical expertise, for example as far as the arrangement of all sorts of different electrodes is concerned. They are consequently only conditionally suitable especially for use at home, for example for the long-term monitoring of infants. In addition, there is the increased risk of falsified data and alarm malfunction because due to the simple electrode structure, it is not possible to make a distinction between medical abnormalities and technical defects (e.g. detached electrodes).
Therefore, there is need for a nonelectric connection between the electrodes connected to the patient and the equipment. Furthermore, due to the galvanic separation of the electrodes from the evaluation station, the safety of the patient is assured as well.
Telemetry systems for biosignals, in connection with which the EKG- or EEG-data tapped on the patient are transmitted via electromagnetic waves (preferably in the infrared range), are described, for example in "Biotelemetrie IX" (publishers: H. P. Kimmich and M. R. Neumann, 1987, pp. 55-58). The data are transmitted in this connection in the one-way mode from the electrodes to the output unit, i.e., without (error) feedback from the receiver to the emitter. A particular drawback in this connection is that the measured values are transmitted as an analog signal, which means they are relatively susceptible to interference, for example with respect to the 50 Hz-ripple and its harmonics.
A further development for telemetric EKG-measurements is described in laid-open patent specification WO 90/08501, where for achieving a higher transmission rate and data safety, the recorded signals are digitalized, coded (preferably according to the Manchester code, or as FSK (frequency shift keying), and then transmitted electromagnetically or by light wave conductor.
In connection with said telemetric method, the signals of the individual electrodes attached to the body are transmitted via cable to an additional emitter unit, which is separately attached to the body, and transmitted from there by radio or light wave conductor to the evaluator station. However, the above-mentioned methods have the drawback that the emitter unit is supplied with current via batteries. The batteries have to assure not only the power supply for the data recording and data processing, but also for the data transmission via radio transmission. Therefore, the batteries have to be replaced frequently, which is connected with drawbacks especially in long-term monitoring. Since the emitter units are relatively large, said methods again limit the freedom of movement of the patient. No details are specified in the above-mentioned references with respect to the structure of the electrodes used for the signal acquisition.
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Measuring probes with HF-energy supply are known, for example from the references DE-OS 32 19 558, U.S. Pat. No. 4,075,632, and WO 92/07505. However, the fields of application of said measuring probes are almost exclusively aimed at the identification of objects, and are implanted for 5 said purpose on the animal or human body. Furthermore, the structure of said device is not suitable for the medical signal acquisition as well as for transmitting such signals, in particular not in connection with a great number of data from one or a plurality of electrode(s), and from a number of 10 patients, if need be. With said methods, the signal transmission takes place almost exclusively via passive telemetry, whereby the measured data are detected in that the measuring probe carries out a modulation absorption in the HF-field of the evaluator station (ES), such absorption acts back on 15 the ES (indirect transmission of information by inductive coupling). Said procedure, however, is suitable only in connection with extremely small spacings between the emitter and the receiver of only a few centimeters (as it is the case especially in connection with implanted probes), and 20 only in the absence of external interferences. Moreover, in connection with said measuring probes, no provision is made for two-way data transmission, i.e., information is transmitted only from the receiver to the transmitter, so that errors in the data transmission can not be compensated, or 25 compensated only highly conditionally.
The invention is based on the problem of making available a reliable monitoring and diagnosis equipment with wireless electrodes, which is suitable for both the use at home and for operation in hospitals. In particular, a safe data 30 transmission of the electrodes is to be assured also when a great number of electrodes are operated simultaneously.
Said problem is solved by the characterizing features of patent claim 1. Preferred embodiments and further developments are specified in the dependent claims. 35
The proposed bidirectional, digital data transmission results in the surprising effect that the data transmission safety is significantly increased. By transmitting redundant information in the data emitted by the electrodes, the evaluator station is capable of recognizing errors and request a 40 renewed transmission of the data. In the presence of excessive transmission problems such as, for example transmission over excessively great distances, or due to obstacles absorbing the high-frequency radiation, the evaluator station is capable also of controlling the data transmission, or to 45 manipulate on its own the data emitted by the electrodes. As control of the data transmission it is possible to consider, for example an adaptation of the transmitting power of the electrode, or a change of the transmission channel. If the signal transmitted by the electrode is too weak, the evaluator 50 station will transmit to the electrode a command, which increases its transmitting power. However, if the signal transmitted by the electrode is superimposed by other sources of interference, the evaluator station, by changing the channel, is capable of attempting securing a flawless and 55 interference-free transmission. Alternatively, the evaluator station can also cause the electrode to change the data format for the transmission, for example in order to increase the redundant information in the data flow. Due to the increased redundancy, transmission errors can be detected and cor- 60 rected more easily. In this way, safe data transmissions are possible even with the poorest transmission qualities. Said measure opens in a surprisingly simple way the possibility of reducing the transmission power of the electrode to a considerable extent. This reduces the energy requirement of 65 the electrodes, so that the latter can be used uninterruptedly over longer periods of time. Due to the reduced transmitting
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power it is possible also to exclude possible biological stresses caused by the electromagnetic waves. Another advantage of the bidirectional digital data transmission lies in the possibility of transmitting test codes in order to filter out external interferences such as, for example, refraction or scatter from the transmission current. In this way, it is possible also to reconstruct falsely transmitted data. Due to the safe data transmission between the electrodes and the evaluator station, the device according to the invention is particularly suitable for use at home such as, for example, far monitoring infants even though no technically trained personnel is available there, as a rule. When used in hospitals, for example for monitoring in intensive care, the device according to the invention offers the special advantage that very many electrodes can be operated at the same time without interferences in one and the same room. Mutual influencing of the electrodes is excluded a priori. In particular, it is possible to program standard electrodes with a great number of sensors via the evaluator station in such a way that such electrodes can be used for special applications, i.e., for special application cases.
The electrodes can be supplied with current by an evaluator station (ES) by means of high-frequency energy transmission (especially in the radio frequency (RF) range). The antennas or optic detectors (e.g. semiconductor diodes) of the electrodes absorb in this connection the high-frequency field (HF-Field) radiated by the evaluator station, the latter being arranged spaced from said electrodes. By means of the power supply unit arranged in the electrode, which unit converts (rectifies) the HF-radiation and stores it, if need be, then supply voltage is then generated for the electrodes.
The device according to the invention can be designed also in such a way that the power supply unit of the electrodes is realized by additional integrated, miniaturized accumulators. A replacement of weak or empty accumulators is not required in connection with the device of the invention because the accumulators are recharged by the high-frequency field radiated by the evaluator station. Charging of the accumulators can be carried out also only temporarily, for example at points in time at which the electrodes are not in use, i.e., outside of the recording of measured values. In this case, the energy for the charging can be transmitted via resonance coupling, for example by means of inductive coupling. Since the accumulators do not have to be replaced, they also can be encapsulated in the electrodes.
Furthermore, it is possible particularly in connection with long-term monitoring to first supply the electrodes with current through the accumulator, and then later—if necessary—supply the electrodes, for example if the accumulators are weak, with current via the emitted HF-frequency field of the evaluator station. In this way, a possible biological stressing of the body by the high-frequency radiation acting on it can be excluded or minimized.
Frequency generation units generate in the electrodes or in the evaluator station the required oscillator frequencies for the emitter units as well as receiving units. Preferably, the frequency generation unit comprises one or a plurality of PLL (phase-locked loop) or FLL (frequency-locked-loop) synthesizers, which generate the various frequencies. The transmission frequencies for the (data) transmission may basically extend from the 100 kHz range (long wave) to the 1015 Hz-range (optical frequencies). For small electrode dimensions, high bit transmission rates and short transmission distances, transmission frequencies in the UHF range, microwave range and above (>10) MHz, however, are particularly suitable.
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