Abstract:
An EEG monitoring apparatus ( 2 ) adapted to be carried continuously by a person being monitored comprises means adapted for measuring at least one EEG signal from the person carrying the apparatus and a signal processing means for analysing said at least one EEG signal and adapted to identify or predict predetermined biological incidents in said person based on said analysis. The EEG monitoring apparatus ( 2 ) further comprises a decision means adapted to decide when information is to be presented to said person and a message selection means for selecting a voice message providing said person with information, as well as an acoustic transducer adapted for presenting the selected voice message to the person. The invention also provides a method for presenting voice messages.

Description:
[0001]    The present application is a continuation-in-part of application PCT/DK2009/050147, filed on Jun. 26, 2009, in Denmark and published as WO 2010/149157 A1. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a portable EEG monitoring apparatus. The invention, more particularly, relates to a portable EEG monitoring apparatus adapted to be carried continuously by a person. The invention furthermore relates to a method of presenting messages in such a portable EEG monitoring device. 
         [0004]    EEG is the commonly used abbreviation for Electro EncephaloGram, EEG monitoring is generally speaking a method of electrically monitoring brain activity of a person. Systems for monitoring EEGs have been known for many years. However with the general technological development, EEG monitoring systems, which may be carried or worn continuously by a person to be monitored, have been devised. 
         [0005]    2. The Prior Art 
         [0006]    One such system is known from the document WO-A1-2006/066577, where blood sugar levels are monitored in a person suffering from diabetes in order to warn against hypoglycaemic attacks. Low blood sugar levels have severe influences on the brain activity and too low blood sugar levels may lead to unconsciousness and even death. The system disclosed WO-A1-2006/066577 is a fully implanted subcutaneous system. The implanted electrodes are via electrical leads connected to a monitoring device capable of detecting the brainwaves characteristic for an imminent hypoglycaemic attack, and issuing a warning in the form of a vibration of the subcutaneous monitoring device. In WO-A1-2006/066577 it is furthermore suggested that the implant may wirelessly communicate with an external unit, which may contain the more power demanding parts of the electronics, so as to obtain a long battery service life of the implanted subcutaneous parts. It is stated that this will also allow an acoustic warning, but WO-A1-2006/066577 does not disclose any details on how. 
         [0007]    Other systems known from e.g. US-A1-2009/0062682 or US-B-6354299 suggest monitoring of brain states using an implant, and the use of voice messages to warn against disorders, such as imminent epileptic seizures, based on the monitored brain states. 
         [0008]    Based on this prior art it is a feature of the present invention, to provide an improved system vis-à-vis the prior art system, in particular regarding the acoustic warning of the person carrying the apparatus. 
       SUMMARY OF THE INVENTION 
       [0009]    The invention, in a first aspect, provides a portable EEG monitoring apparatus, said apparatus comprising: EEG pick-up means adapted for measuring at least one EEG signal from the person carrying the apparatus, a signal processing means for analysing said at least one EEG signal and adapted to identify or predict predetermined biological incidents in said person based on said analysis, a decision means adapted to decide when information is to be presented to said person, a message selection means for selecting a voice message providing said person with information, and an acoustic transducer adapted for presenting the selected voice message to the person, where said apparatus is adapted to present the voice message in the ear of the person. 
         [0010]    The invention, in a second aspect, provides a method for presenting voice messages in a portable EEG monitoring apparatus, said method comprising measuring at least one EEG signal from the person carrying the apparatus using an EEG pick-up means; analysing said at least one EEG signal using a signal processing means adapted to identify or predict predetermined biological incidents in said person based on said analysis; deciding, using a decision means, when information is to be presented to said person; selecting, using a message selection means, a voice message for providing said person with information; and presenting, in the ear of the person, the selected voice message to the person using an acoustic transducer. 
         [0011]    Using a voice message rather than, e.g. a simple warning tone, has many advantages. A major advantage, however, is that a voice message, such as a spoken warning is far more pervasive in getting the attention of the person addressed, and far easier for the person to respond correctly to. Bearing in mind that the purpose of the EEG monitoring is in first instance to warn the person about threatening biological incidents such as imminent hypoglycaemic seizure, it is very likely that the warning issued by the apparatus is issued at a time where the person is already no longer at his full mental capacity, or even on the verge of unconsciousness. A voice message is in this situation not only far more efficient in alerting the person, but may moreover actually contain direct instructions regarding the corrective actions to be performed, in order to avoid the threatening condition. Thus, the person who may already be partially mentally incapacitated, will not only get an alarm at a time where he is no longer capable of remembering what the correct corrective actions are and how to perform these, but will get a voice message reminding him of the appropriate corrective actions. 
         [0012]    According to a preferred embodiment said voice message relates to said biological incident. 
         [0013]    Presenting the message directly in the ear of the user is advantageous in that it reduces external disturbances such as ambient noise. Moreover, it is advantageous in that it allows the EEG monitoring apparatus to further comprise the functionalities of a hearing aid, or to form part of a hearing aid. 
         [0014]    According to a preferred embodiment of the first aspect of the invention, said voice messages are stored in the apparatus. Storing the voice messages in the apparatus obviates the need of carrying any further devices, or the need of a synthetic voice generator. 
         [0015]    According to a further preferred embodiment of the first aspect of the invention, the voice messages are formatted into a format suitable for storage and replay in the apparatus. This reduces the need for storage space, and may thus allow for an overall size reduction, or the storage of a larger variety of voice messages. 
         [0016]    According to another embodiment of the first aspect of the invention, said voice messages have been edited in accordance with the hearing capabilities of said person. Editing the voice messages allow built-in adaptation of the messages to a specific hearing loss of the person. This, in turn, increases the intelligibility of the voice message. 
         [0017]    According to yet another embodiment of the first aspect of the invention, the apparatus comprises means for adjusting the presented voice message to the current ambient acoustic noise level when presenting the message. This further enhances intelligibility of the message. 
         [0018]    According to a further embodiment of the first aspect of the invention, the apparatus comprises means for allowing the person carrying the apparatus to store messages therein in accordance with the persons own choice. This allows the person carrying the apparatus to choose straight forward easy to understand messages. 
         [0019]    According to another embodiment of the first aspect of the invention, the apparatus comprises means for the person carrying the apparatus to acknowledge the presented message. Hereby it becomes possible to ensure that the person carrying the apparatus has actually heard the message, and if necessary repeat the message until it has been acknowledged, possibly with increased volume. 
         [0020]    According to yet another embodiment of the first aspect of the invention, the apparatus is further adapted to present voice messages relating to the handling of the apparatus. This aids the person carrying the apparatus in the handling and use thereof, e.g. when placing the apparatus in the ear. 
         [0021]    Embodiments of the method according to the second aspect of the invention generally provide the same advantages as the embodiments according to the first aspect. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The invention will now be described in greater detail based on non-limiting exemplary embodiments and the drawing, on which: 
           [0023]      FIG. 1  depicts a head of a person with an EEG monitoring apparatus according to an embodiment of the invention, 
           [0024]      FIG. 2  depicts a block diagram of the EEG monitoring apparatus according to  FIG. 1 , 
           [0025]      FIG. 3  illustrates the storage and retrieval of messages in the EEG monitoring apparatus of  FIG. 2 , and 
           [0026]      FIG. 4  depicts a state diagram of the user interface of the EEG monitoring apparatus according to  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]      FIG. 1  schematically shows a head  1  of a person carrying an EEG monitoring apparatus  2  according to an embodiment of the invention. The EEG monitoring apparatus  2  comprises an implant unit  3  for measuring EEG&#39;s. The implant unit  3  is located subcutaneously behind the ear  4  of a person. The implant unit  3  comprises an electronics part  5  and an EEG pick-up means  6  such as probe with at least two electrodes (not shown) for picking up electrical EEG signals from the brain of the person. The electronics part  5  of the implant unit  3  comprises the necessary electronics for sampling the EEG signals measured by the electrodes of the EEG pick-up means  6  and transmitting them wirelessly to an external unit  7  forming part of the EEG monitoring apparatus  2 . Preferably, the energy supply to the implant unit  3  is received inductively from the external unit  7 , so that the implant unit  3  has a long service life, not constrained by battery capacity, which is advantageous since a replacement of the battery would necessitate a surgical procedure for replacement of the whole implant unit  3 . 
         [0028]    As can be seen, the external unit  7  may resemble a Behind-The-Ear hearing aid (BTE hearing aid), comprising a housing part  8 , which in normal use is placed behind an ear  4  of the person carrying the EEG monitoring apparatus  2 . Like a BTE hearing aid, the housing part  8  is connected to an earplug  9  in the ear canal of the person via an intermediate connection  10 . This could be a traditional sound tube leading to an earplug, or an electrical cord leading to a Receiver In The Ear type earplug (RITE earplug). This allows the external unit  7  to give off messages, such as alarms or warnings, into the ear  4  of the person carrying the EEG monitoring apparatus  2 . 
         [0029]    As indicated, the EEG monitoring apparatus  2  may optionally include a peripheral device  11 , which, as will be explained later, may comprise additional and possibly more energy consuming electronic storage space for data. 
         [0030]    Turning now to  FIG. 2 , the internal details of the external unit  7  of the EEG monitoring apparatus  2  are schematically shown. The external unit  7  comprises a health state monitor  12 , comprising means for analysing an EEG signal received wirelessly from the implant unit  3 , and for detecting anomalies in said EEG signal, in order to warn the person carrying the EEG monitoring apparatus  2  against health threatening conditions, such as e.g. hypoglycaemia or epileptic seizures. How this analysis is performed is not relevant for the present invention and will not be dealt with any further. 
         [0031]    If a health threatening condition is detected, the health state monitor  12  sends an appropriate signal to a device operating controller  13 . The device operating controller  13  is also adapted for receiving other input such as a signal indicating low battery level from a battery monitor  14  monitoring the battery  15  supplying the EEG monitoring apparatus  2 , and a user input signal from a user button  16  comprising e.g. an electromechanical key switch  17 . 
         [0032]    The device operating controller  13  selects an appropriate message and settings for the message and sends a corresponding signal to an audio generator  18 , which generates a message signal for an output converter  19 , such as a DAC generating an output signal for an output transducer, such as a loudspeaker  20 . As indicated above the loudspeaker could be placed in the housing  8  of the external device or it could be placed in the earplug  9 , but it should be noted that the present invention is not limited to the use in BTE type devices, it could also be implemented in an In-The-Ear earplug (ITE earplug) or any other type of earplug known e.g. from hearing aids. The message signal or data relating thereto may pre stored in a non-volatile memory, such as an EEPROM  21 . 
         [0033]    Preferably, the EEG monitoring apparatus  2  also comprises means for monitoring ambient sound pressure level. In the illustrated embodiment, such means comprise a monitor microphone  22  delivering a signal to an input converter  23  such as an ADC. The input converter  23  delivers a signal to a sound pressure level monitor  24 . The sound pressure level monitor  24  detects the ambient sound pressure level, and delivers a corresponding signal to the audio generator,  18 , allowing the audio generator to adapt the volume settings for the signal to the output converter  19  in accordance with the ambient sound pressure level. Thus, it is ensured that the message signal delivered by the loudspeaker  20  has a volume level allowing it to be easily heard by the person carrying the EEG monitoring apparatus  2 . At the same time it is ensured that the message is not presented with an excessive loudness in quiet surroundings, which could be both disturbing and uncomfortable for the person carrying the EEG monitoring apparatus  2 . Evidently, the sound pressure level monitor need not be operative at all times. It is sufficient to sample the current sound pressure level for just a short time before presenting the message. Thus, power is saved. 
         [0034]      FIG. 3  illustrates various messages stored in the non-volatile memory  21 . Only five messages are illustrated, i.e. messages #1 to #4 and the last message #N, comprising typical warnings, such as “System OK”, “Hypoglycaemia Warning”, “Low Battery”, “Press button to acknowledge” and “System Failure”. These messages are retrieved from the non-volatile memory  21  by means of a control logic and address generator  25  in the device operating controller  13 , addressing a desired message, or rather the data defining it, in the non-volatile memory and causing the corresponding message data to be sent to the audio generator  18 , which produces the output signal to the output converter  19  on the basis thereof. 
         [0035]    Depending on considerations such as the available storage, power consumption etc., the data defining the desired message and stored in the non-volatile memory may differ. 
         [0036]    One way of storing the messages would be uncompressed digital audio, where the entire data stream necessary for the audio generator  18  to generate the signal to the output converter  19  is stored. In that case the audio generator  18  could generate a pulse code modulated signal for the output converter  19 , which turns the pulse code modulated signal into an analog signal. However, because the dynamic range of speech is quite wide, the pulse code modulated signal could be a weighted signal such as an A-law or MU-law weighted signal, where the dynamic range is compressed before storage. The audio generator  18  would in that case also perform a corresponding expansion of the message signal. 
         [0037]    An alternative could be compressed audio as is known from speech or audio codecs, where the compressed data signal is stored as data in the memory. Examples of such speech and audio codecs are; MPEG-1 (mp3), described in the standard ISO/IEC-11172 part 3, DPCM (Differential Pulse Code Modulation), ADPCM (Adaptive Differential Pulse Code Modulation), described in the standard ITU G.726, subband-ADPCM as described in the standard ITU G.722, or speech codecs as described in standards ITU G.729 or ITU G.728. 
         [0038]    Also, instead of compressed audio based on a real speech signal, synthetic speech could be used. Synthetic speech can be generated from symbol-linguistic representations, such as phonemes or other symbol representation of basic building blocks of a speech signal. In that case these symbols are stored in the non-volatile memory  21 , and the audio generator comprises a synthesizer, which synthesizes waveform signals based on the symbols. Such synthesizing will typically be based on a mapping from the symbol representation to waveform signals based on segments of a sampled speech signal. 
         [0039]    In addition to the above methods, or possibly a combination thereof, the EEG monitoring apparatus may also comprise means for generating non-speech sounds, such as simple sounds like pure tones, or “pling”, “boing”, “bleep” or the like or sounds resembling musical instruments. Such sounds may be generated by an audio generator  18  comprising one or more tone generators and/or filters, e.g. impulse response filters or simple filters. 
         [0040]      FIG. 4  shows a state diagram of the user interface of the EEG monitoring apparatus according to the invention. The diagram is simplified to illustrate only the most essential messages, but as will be understood from  FIG. 3  there can be many more messages, adding of course to the complexity of the interface. 
         [0041]    In  FIG. 4  the following texts are used: 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 Message Mnemonic 
                 Message 
               
               
                   
                   
               
             
             
               
                   
                 SysOK 
                 “System OK” 
               
               
                   
                 LowBat 
                 “Low battery” 
               
               
                   
                 HealthStateWarn 
                 “Hypoglycaemia warning” 
               
               
                   
                 KeyToAck 
                 “Press key to acknowledge 
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 Timer 
                 Timer Usage 
               
               
                   
                   
               
             
             
               
                   
                 T1 
                 Timer for repeating unacknowledged messages 
               
               
                   
                 T2 
                 Timer for repeating warnings from health state monitor 
               
               
                   
                 T3 
                 Battery alarm timer 
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 User Interface Input 
                 Description 
               
               
                   
                   
               
             
             
               
                   
                 UserPressKey 
                 User key press 
               
               
                   
                 LowBat 
                 Low battery signal from battery monitor 
               
               
                   
                 HealthStateSig 
                 Signal from health state monitor 
               
               
                   
                   
               
             
          
         
       
     
         [0042]    The state diagram of  FIG. 4  will now be described. However, for full explanation, reference to apparatus parts not shown in  FIG. 4  is also made in the following description. Please refer to  FIGS. 1 and 2  for those reference numerals not found in  FIG. 4 . 
         [0043]    Starting at the top of  FIG. 4  the EEG monitoring apparatus  2  boots in box  100  when switched on. During booting, the EEG monitoring apparatus performs a number of self-tests, such as testing the functioning of the electrodes of the EEG pick-up means  6 , and the communication link between the implant unit  3  and the external device  7 . If the self-test is successful a true flag is set and, in box  101 , the device operating controller  13  sends SysOK to the audio generator  18 , which retrieves the message “System OK” in the non-volatile memory and presents it to the person carrying the EEG monitoring apparatus  2 , via the output converter  19  and the speaker  20 . The person carrying the EEG monitoring apparatus  2  thus receives confirmation that the EEG monitoring apparatus  2  is operating and functional. After the “System OK” message has been sent, the EEG monitoring apparatus  2  enters its normal state in box  102 . In box  102 , the person wearing the EEG monitoring apparatus can at any time activate the user push button  16  by pressing the key switch  17 , which will lead to a new self-test and message in box  101 . 
         [0044]    If at any time the battery monitor  14  detects low battery, it sends the low battery signal, LowBat, to the device operating controller  13 , or preferably sets it high as a flag for the device operating controller  13  to detect. Provided a timer T 3  is not running, the device operating controller  13  sends LowBat to the audio generator  18 , which retrieves the message “Low battery” in the non-volatile memory and, in box  103 , presents it to the person carrying the EEG monitoring apparatus  2 , via the output converter  19  and the speaker  20 . At the same time the timer T 3  is started. If the timer T 3  is still running, i.e. has not timed out, LowBat is not sent to the to the audio generator. By proper selection of the time value of T 3 , the person carrying the EEG monitoring apparatus is thus prevented from hearing the “low battery” messages so frequently that it annoys him. Thus, at intervals corresponding to T 3  the person carrying the EEG monitoring apparatus is repeatedly reminded to change the battery. When he eventually does so, the EEG monitoring apparatus  2  boots again in box  100 . 
         [0045]    If at any time the health state monitor  12  detects imminent hypoglycaemia, it sends the hypoglycaemia warning signal, HealthStateSig, to the device operating controller  13 , or preferably sets it high as a flag for the operating controller  13  to detect. Provided a timer T 2  is not running, the device operating controller  13  sends HealthStateWarn to the audio generator  18 , which retrieves the message “Hypoglycaemia warning” in the non-volatile memory and, in box  104 , presents it to the person carrying the EEG monitoring apparatus  2  via the output converter  19  and the speaker  20 . At the same time a timer T 1  is started. If the person carrying the EEG monitoring apparatus  2  activates the user push button  16  by pressing the key switch  17 , the device operating controller receives the input UserKeyPress, which acknowledges that the user has heard the message presented to him. At the same time the timer T 2  is started in box  105 . If, in box  102 , the timer T 2  is still running, i.e. has not timed out, the user interface does not proceed from box  102  to  104 , and the person carrying the EEG monitoring apparatus is thus prevented from hearing the “Hypoglycaemia warning”, messages so frequently that it annoys him, if he knows he does not yet need to take action or he is not in a position to take such action. 
         [0046]    If the person carrying the EEG monitoring apparatus  2  does not acknowledge the message “Hypoglycaemia warning”, the timer T 1  will eventually time out and the interface will proceed from box  104  to  106 . In box  106 , the device operating controller  13  sends HealthStatWarn and KeyToAck to the audio generator  18 , which sequentially retrieves the messages “Hypoglycaemia warning” and “Press key to acknowledge” and presents them to the person carrying the EEG monitoring apparatus  2  via the output converter  19  and the speaker  20 . At the same time the timer T 1  is restarted. These two messages will then be repeated at intervals corresponding to the value of T 1 , which is preferably relatively short compared to T 2 , until either the person carrying the EEG monitoring apparatus  2  eventually activates the user push button  16  by pressing the key switch  17 , or the signal or flag HealthStateWarn goes low, e.g. because the person carrying the EEG monitoring device has taken appropriate actions. In the former case, the interface proceeds to box  105 , where the timer T 2  is started, and back to box  102  where it remains until T 2  times out as described above. In the latter case where HealthStateSig goes low, there is no danger any more and the interface returns to box  102  where it remains until changes occur. That is to say until the flags HealthStateSig or LowBat go high again, or until the user activates the push button  16  by pressing the key switch  17  in order to perform a self-test. 
         [0047]    With such a user interface the EEG monitoring apparatus  2  gives off the alarm or warning to the person wearing the EEG monitoring apparatus  2 , and does this repeatedly until the person has heard and responded to the warning. Since the alarm or warning is related to a life threatening condition it may be important to repeat the message frequently. A typical value for T 1  could thus be less than a minute, e.g. 15 seconds. A typical value for T 2 , where the person carrying the EEG monitoring apparatus  2  has acknowledged the messages and is expected to take proper action, should be longer, e.g. several minutes. A typical value for T 2  could be 10 to 15 minutes. T 3  for the battery alarm could depending of the criteria selected for the battery alarm be longer e.g. 1 to 2 hours or more. 
         [0048]    In order to ensure that the person carrying the EEG monitoring apparatus  2  is not just missing the message by not hearing it, the volume could be increased with each repetition until it is acknowledged. 
         [0049]    Though the interface above has been described only in relation to a simple structure with a few warning messages, the skilled person will realise that means for providing access to further messages could be realised, e.g. by activating the push button  16  by repeatedly pressing the key switch  17  twice or multiple times. The signal sent from the push button  16  to the device operating controller  13  could depend on the number of times the key switch  17  is pressed. This could gain access to menu points and messages, where more data is provided to the person carrying the EEG monitoring apparatus  2 . This is particularly interesting if the EEG data is logged over time. In such cases the user may learn more about when he typically has many warnings or the like. Also, it may provide access to the settings of the EEG monitoring apparatus  2 , e.g. allowing the user to change alarm threshold, warning intervals, volume settings etc. Furthermore, the user may even use the menu to upload information externally to the peripheral device  11 , with larger storage capacity, so as to store information about his daily behaviour in terms of blood sugar, so as to keep a diary about events and the like, or event to learn how to modify his behaviour. 
         [0050]    The invention has been described above with reference to various specific embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims. In particular the skilled person will realise that instead of using a subcutaneous implant, it will also be possible to implement the messages in a fully external EEG monitoring apparatus, e.g. in an earplug or BTE device using external electrodes in contact with the skin, as well as in an external EEG monitoring apparatus having a wired connection to the implant. 
         [0051]    The skilled person will also realise that sufficient electronic storage space may be provided in the EEG monitoring apparatus to store generic speech messages which may be altered or interchanged with other messages by means of a peripheral device  11  such as a mobile telephone. 
         [0052]    Messages may also be provided for guiding the person carrying the EEG monitoring device through the mounting process, when he puts it on and starts carrying it.