WO2010029393A1

WO2010029393A1 - A wireless transmission method for physiological signals

Info

Publication number: WO2010029393A1
Application number: PCT/IB2008/055612
Authority: WO
Inventors: Raymond Gass; Michel Le Creff
Original assignee: Alcatel Lucent
Priority date: 2008-09-12
Filing date: 2008-09-12
Publication date: 2010-03-18
Also published as: EP2341817A1

Abstract

This method comprises the steps of inserting N respective values of N physiological signals into N fixed fields (Byte 1, Byte 3,..., Byte 23) of a fixed length frame (F), and then sending each frame (F) in a transmission channel adapted for transmitting a voice signal in synchronous connection oriented link (SCOL). Each frame (F) comprises a synchronization pattern (SYNC1, SYNC2,... SYNC22) comprising N separate fixed fields (Byte 0, Byte2,..., Byte 22) that are interleaved with N fixed fields (Byte 1, Byte 3,..., Byte 23) that respectively contain the N respective values of N physiological signals.

Description

A wireless transmission method for physiological signals

BACKGROUND OF THE INVENTION Field of the invention The present invention generally relates to a wireless transmission method for physiological signals. It can be used, in particular, for transmitting physiological signals from a patient to a distant processing unit, or to a distant patient file database, via a voice dedicated telecom network, such as a public switched telephone network, a cellular mobile network, or the telephone network of a hospital.

These signals may be auscultation sounds, electrocardiograms (ECG), electro-encephalograms, etc. For instance, an ECG is a graphical representation of heart electrical activity in a patient. ECG systems utilize up to ten electrodes placed on a patient in specific locations to detect electrical impulses generated by the heart during each beat. Typically, these electrical impulses or signals are detected by and directly transferred from the electrodes to a stationary ECG monitor via multiple cables or wires The ECG monitor performs various signal processing and computational operations to convert the raw electrical signals into twelve standardized ECG signals that can be displayed on a monitor, or printed out for review by a physician. Systems using multiple cables or wires are cumbersome and uncomfortable for the patient, and require a significant amount of set up time. The document US 20040073127 describes a system for wirelessly transmitting physiological data, comprising: a body electronics unit for acquiring physiological data from electrodes, and a base station having a plurality of terminals for transmitting the physiological data to a monitor.

They are linked by a Bluetooth radio link.

Electrodes are placed on the patient^'s body and are linked to the body electronics unit. The Bluetooth transceiver of the electronics unit and the Bluetooth transceiver of the base station are paired or coupled by means of a token key. The electrical signals from the heart are transformed by the body electronics unit, from analog signals to digital signals. There are ten channels for the physiological signals. Three of the channels correspond to LA, RA, and LL electrodes and are sampled at 16 kHz The seven remaining channels correspond to V and V.sub.1 -V.sub.6 electrodes and are sampled at 4 kHz. The channels corresponding to the LA, RA, and LL electrodes are sampled at a faster rate in order to detect fast transients (i.e. , pacemaker pulsesi in the data from these channels.

The body electronics unit transmits the digital signals to the base station via the Bluetooth radio link, in a range of ten meters or so. The physiological data are sent in variable length packets on an asynchronous link, called asynchronous connectionless link, in the Bluetooth terminology. The base station transforms the digital signals into analog signals and transmits the analog signals to an ECG monitor, via cables. The ECC monitor processes the analog signals into standardized ECG signals that can be displayed on the monitor.

It would be advantageous to transmit physiological signals from a patient to a distant processing unit, for consulting a distant practitioner, or to a distant patient file database for storing physiological data into a patient's file, via a voice dedicated telecom network, such as a public switched telephone network, a cellular mobile network, or the telephone network of a hospital.

The system described in the document US 20040073127 is not adapted for such a transmission because the asynchronous connectionless link is not directly compatible with a voice dedicated telecommunication network. Thus, there is a need to provide a technical solution more adapted for transmitting physiological signals from a patient to a distant processing unit, or to a distant patient file database via a voice dedicated telecommunication network.

This can be solved by applying the method according to the invention.

SUMMARY OF THE INVENTION

The object of the invention is a wireless transmission method for at least N physiological signals characterized in that it comprises the steps of inserting N respective values of N physiological signals into N fixed fields of a fixed length frame, and then sending each frame in a transmission channel adapted for transmitting a voice signal in a synchronous mode. Thanks to the fixed length frame and to the transmission channel adapted for transmitting a voice signal in a synchronous mode, this method is quite compatible with the voice dedicated telecommunication networks, including voice over IP networks,

According to a peculiar embodiment of the method according to the present invention, said transmission channel is a synchronous connection oriented link.

According to a preferred embodiment, the method further comprises the step of inserting in each frame a synchronization pattern comprising N separate fixed fields that are interleaved with N fixed fields that respectively contain the N respective values of N physiological signals, Thanks to this characteristic, the synchronization of a reception unit is quicker and more stable, in comparison with the synchronization of a reception unit by a synchronization pattern that would be constituted by a single field placed at the beginning of each frame. Other features and advantages of the present invention will become more apparent from the following detailed description of embodiments of the present invention, when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to illustrate in detail features and advantages of embodiments of the present invention, the following description will be with reference to the accompanying drawings. If possible, like or similar reference numerals designate the same or similar components throughout the figures thereof and description, in which:

• Figure 1 represents a first example of transmission system using the method according to the invention for transmitting physiological signals to a distant processing unit via a public land mobile telephone network. - Figure 2 represents a second example of transmission system using the method according to the invention for transmitting physiological signals to a distant reception unit via the telephone network of a hospital.

- Figure 3 represents an example of transmission frame implementing the method according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first example of transmission system represented on figure 1 aims at transmitting up to twelve ECG signals, and some additional information, via a telephone network such as a public land mobile telephone network PLMN. These ECG signals do not represent the voltages captured by electrodes. They are derived from these voltages by a standardized processed. This first example comprises:

- A portable transmission unit 1 which is attached to the patient's body, on an arm for instance, and which is connected by wires to various sensors, such as temperature sensor, blood pressure sensor, an oximeter, etc, and to ten electrodes E1 ,..., E10, for capturing ten voltages. The transmission unit 1 derives twelve standardized ECG signals from the ten voltages supplied by the ten electrodes. The patient is at home, for instance. ■ A processing unit composed of a GSM mobile phone 2 comprising a Bluetooth transceiver is near the patient. Its Bluetooth transceiver is connected to the portable transmission unit 1. Its GSM transceiver is connected to a base station BS of the public land mobile telecommunication network PLMN. Of course, it could be replaced by a personal computer, or a smartphone, comprising a GSM interface and a Bluetooth interface.

• A reception unit 3, located in a distant hospital, for instance. A classical GSM voice communication is established between the mobile phone 2 and the reception unit 3 via the public land mobile telecommunication network PLMN and via the public switched telephone network PSTN.

In this example, the portable transmission unit 1 comprises: - An amplification and filtering unit AFU that is adapted to receive and amplify the signals supplied by sensors, and by the ECG electrodes E1 ,...,E1O.

- A sampling unit SU for sampling the amplified signals, digitizing them, deriving the twelve standardized ECG signals and inserting them into frames that will be described below.

- A classical Bluetooth transceiver BT transmitting the frames generated by the sampling unit SU, on a synchronous connection oriented Bluetooth link

SCOL.

In the GSM mobile phone 2, the Bluetooth transceiver is adapted to receive frames on the synchronous connection oriented Bluetooth link SCOL, and to forward these frames to the distant reception unit via a classical GSM voice channel established between the mobile phone 2 and the GSM base station BS of the public land mobile network PLMN.

The reception unit 3 comprises a server S, a signal restoration unit RU, and an output device, such as an ECG monitor or a personal computer. The server S comprises a softphone that enables it to place /receive phone calls via a public switched telephone network PSTN. This latter is linked to the public land mobile telecommunication network PLMN. The server S receives frames that contain digital coding of the analogue signals representative of the ECG signals. The restoration unit RU extracts, from the frames, the respective values of the twelve ECG signals, and it adapts them to the output device OD.

The article A 1-V CMOS PREPROCESSING CHIP FOR ECG MEASUREMENTS, Kimmo Lasanen and Juha Kostamovaara, University of OuIu, Department of Electrical and Information Engineering, P.O.BOX 4500, 90014 University of OuIu, FINLAND, describes an example of amplifying and filtering circuit for a voltage captured by an ECG electrode. This circuit can be used for building the amplification and filtering unit AFU.

The building of the sampling unit SU and of the restoration unit RU is within the scope of a man skilled in the art when he/she knows the structure of the frame that will be described below.

A Bluetooth radio link uses a spread spectrum, frequency hopping, full- duplex signal at up to 1600 hops/sec. The signal hops among the radio frequency channels at 1 MHz intervals to provide a high degree of interference immunity. Information is exchanged through packets. Each packet is transmitted on a different hop frequency. A packet nominally covers a single slot, but can be extended to cover up to five slots, if the link is an asynchronous connectionless link. Data in a packet can be up to 2,745 bits in length.

There are currently two types of data transfer between devices: • SCO (synchronous connection oriented*

• ACL (asynchronous connectionless*.

In a Bluetooth piconet, there can be up to three SCO links of 64.000 bits per second each. To avoid timing and collision problems, the SCO links use reserved slots set up by the master. Masters can support up to three SCO links with one, two or three slaves Slots not reserved for SCO links can be used for ACL links. One master and slave can have a single ACL link. ACL is either point-to-point (master to one slave) or broadcast to all the slaves. ACL slaves can only transmit when requested by the master. Though, an ACL link would be best adapted for transmitting data, the method according to the invention uses an SCO Bluetooth link, because it is designed to carry a voice signal. So it is quite compatible with any voice dedicated telecommunication network.

Each time slot is 625 microseconds in length. In the time slots, the master (i.e.. the base station ) and slave (i.e. , the body electronics unit on the patient) can transmit packets. A time division duplexing scheme is used where a master and a slave alternatively transmit in a synchronous manner. The master shall start its transmission in even numbered time slots only, and the slave shall start its transmission in odd numbered time slots only. The packet start shall be aligned with the slot start. Packets transmitted by the master or the slave may extend over or up to five time slots. Due to packet types that cover more than a single slot, master transmission ma> continue in odd numbered slots and slave transmission may continue in even numbered slots.

A channel is represented by a pseudo-random hopping sequence hopping through the radio frequency channels. The hopping sequence is unique for a piconet comprising up to seven Bluetooth slave devices and a Bluetooth master device. The hopping sequence is determined by the Bluetooth device address of the master (e.g., each base station has a transceiver that is allocated a unique 48-bit Bluetooth device address). The phase in the hopping sequence is determined by the Bluetooth clock of the master. The channel is divided into time slots where each slot corresponds to an RF hop frequency. Consecutive hops correspond to different RF hop frequencies AU Bluetooth units participating in a piconet are time and hop synchronized to the channel,

A data channel hops randomly 1 ,600 times per second between the 79 (or 23) RF channels Each channel is divided into time slots 625 microseconds long, A piconet comprises a master and up to seven slaves. The master transmits in even time slots, slaves in odd time slots, The RF hop frequency shall remain fixed for the duration of a packet. For a single packet, the RF hop frequency to be used is derived from the current Bluetooth clock value. For a multi-slot packet, the RF hop frequency to be used for the entire packet is derived from the Bluetooth clock value in the first slot of the packet. The RF hop frequency in the first slot after a multi- slot packet shall use the frequency as determined by the current Bluetooth clock value, If a packet occupies more than one time slot, the hop frequency applied shall be the hop frequency as applied in the time slot where the packet transmission was started, The hoping sequence selection procedure consists of selecting a sequence and mapping this sequence on the hop frequencies, The type of sequence selected mostly depends on the state of the devices communicating, Every Bluetooth unit has an internal system clock, which determines the timing and hopping of its transceiver. The Bluetooth clock is derived from a free running native clock, which is never adjusFed and is never turned ^"off. For synchronization with other units, only offsets are used that, added to the native clock, provide temporary Bluetooth clocks which are mutually synchronized, It should be noted that the Bluetooth clock has no relation to the time of day; it can therefore be initialized at any value, The Bluetooth clock provides the heart beat of the Bluetooth transceiver. Its resolution is at least half the transmission or reception slot length, or 312.5 microseconds. The clock has a cycle of about a day.

The timing and the frequency hopping on the channel of a ptconet are determined by the Bluetooth clock of the master. When the piconet is established, the master clock is communicated to the slaves. Each slave adds an offset to its native clock to be synchronized to the master clock. Since the clocks are free running, the offsets have to be updated regularly. This offset is updated each time a packet is received from the master: by comparing the exact receiver timing of the received packet with the estimated receiver timing, the staves correct the offset for any timing misalignments,

Frequency hopping is accomplished with the use of a fast settling phase locked loop (PLL). The data transmitted has a symbol rate of 1 Ms ⁷S (mega samples per second). The data are conveyed in packets. Each packet consists of 3 entities: the access code, the header, and the payload. The access code and header are of fixed size: 72 bits and 54 bits respectively. The payload can range from zero to a maximum of 2745 bits. Each packet starts with an access code. If a packet header follows, the access code is 72 bits long; otherwise the access code is 68 bits long, This access code is used for synchronization, DC offset compensation, and identification. The access code identifies all packets exchanged on the channel of a piconet: all packets sent in the same piconet are preceded b> the same channel access code. In the receiver of the Bluetooth unit, a sliding correlator correlates against the access coαe ana triggers wnen a threshold is exceeded. This trigger signal is used to determine the receive timing.

Before transmission, both the header and the payload are scrambled with a data whitening word in order to randomize the data from highly redundant patterns and to minimize direct current bias in the packet. The scrambling is performed prior to field error control (FEC) encoding. At the receiver, the received data is descrambled using the same whitening word generated in the recipient. The descrambling is performed after FEC decoding. After transmission, a return packet is expected

N. times.625 microseconds after the start of the transmitter burst where N is an odd, positive integer. N depends on the type of the transmitted packet. To allow for some time slipping, an uncertainty window is defined around the exact receive timing. During normal operation, the window length is 20 microseconds, which allows the receiver burst to arrive up to 10 microseconds too early or 10 microseconds too late. In a preferred embodiment of the method according to the invention, the sampling rate is preferably equal to 25OHz.

The samples of the physiological signals are coded on eight bits, with the law A or Mu which are classically used for coding voice samples. For twelve EGC signals, sampled at 250 Hz, the resulting bit rate is 24 Kilobits per second. It can be easily carried by a voice channel at 64 Kilobits per second, in particular by a Bluetooth synchronous connection oriented (SCO) channel which is a symmetric point-to-point link between a master and a single slave, classically used for a voice signal. The master maintains a SCO channel by reserving time slots at regular intervals. A classical Bluetooth transceiver can support up to three parallel 64 Kilobits/ s SCO channels.

The use of a synchronous connection oriented channel provides the advantage oi being directly compatible with any public switched telephone network, any public land mobile network, and any private telephone networκ oτ a nospitai Nowadays a hospital telecommunication network is based on the

Internet Protocol, and is generally separated in two parts: one supporting data, and one supporting telephony. The access to the part supporting data is forbidden for protecting the security of confidential data, The part supporting telephony comprises at least one virtual local area network

(VLAN) supporting voice over IP (VOIP), and it is more easily accessible. So it is advantageous to be able to send the physiological signals in Real-time

Transport Protocol (RTP> containers via the part supporting VOIP telephony. Classically, in networks offering VoIP services there are several VLAN that are dedicated to VoIP traffic (Fax, modem).

Figure 2 represents a second example of transmission system using the method according to the invention for transmitting physiological signals to a distant reception unit via the telephone network HN of a hospital. This example comprises:

- A portable transmission unit 1 , that may be identical to the one described above, is attached to a patient's arm, for instance, The patient is a hospital room. The portable transmission unit 1 is connected by wires to various sensors, such as temperature sensor, blood pressure sensor, oximeter sensor, etc, and to ten electrodes E1 ,..., E10. The transmission unit 1 derives twelve standardized EGC signals from the ten captured voltages. As in the previous example, the portable transmission unit 1 transmits frames via a Bluetooth transceiver BT, on a synchronous connection oriented Bluetooth link SCOL. ■ A personal computer PC comprising a Bluetooth transceiver is placed near the patient and is connected to the portable transmission unit 1 via the connection oriented Bluetooth link SCOL. The personal computer PC comprises a softphone. It enables the personal computer PC to place/ receive phone calls v ia the hospital telephone network HN.^" - A reception unit 3, that may be identical to the one described above, is located somewhere in the hospital, and it comprises a sewer S, a signal restoration unit RU, and an output device OD, such as a ECG monitor or personal computer. The server S comprises a softphone linked to an extension of the hospital telephone network HN. It enables the server S to place/receive phone calls via the hospital telephone network HN.

A classical Real-time Transport Protocol voice over IP communication has been established between the personal computer PC and the reception unit 3 via the hospital telecommunication network HN.

The Bluetooth transceiver of the personal computer PC receives the frames carrying the physiological signals, sent by the transmission unit 1 on the connection oriented Bluetooth link SCOL. The personal computer PC forwards these frames, as it would do with a voice signal, to the server S, via the hospital telephone network HN, over Real-time Transport Protocol (RTP) channels that are dedicated for Voice over IP services.

In both examples, the frames have a fixed number of bytes, chosen so that it is compatible with a voice channel of a telecommunication network, with a bit rate equal to 64 Kilobιts/s.

The method according to the invention consists in inserting N respective values of N respective samples of N physiological signals into N fixed fields of a fixed length frame, and then sending each frame in a transmission channel adapted for transmitting a voice signal in a synchronous mode.

Figure 3 represents an example of transmission frame F implementing the method according to the invention, for twelve ECG signals and other phy siological data. HreteraDiy, eacn trame compπseT32^"fields,^~each^~field being^{^}one byte long! These fields are referenced Byte 0, ..., Byte 31 , on the figure 3. Thus a channel with 64 Kilobits/ s can carry 250 such frames per second, each frame having a fixed duration of 4 milliseconds.

According to a first embodiment, the values of twelve ECG signals are sampled at 250Hz, and are digitized on 8 bits, with a non linear coding law, such as the classical law A or Mu. So it is possible to carry the 24 Kbits/s representing the values of twelve ECG signals sampled at 250Hz, and digitized on 8 bits, and some bit rate remains available for carrying supplementary information. In addition, the values captured by various sensors can also transmitted,

In each frame F, the uneven bytes Byte 1 , Byte 3, ..., Byte 21 , Byte 23 are used for carrying the values of samples of twelve ECG signals, The number of connected electrodes may be reduced in some cases, and so the number of ECG signals may be less than twelve. In such a case, some of the fields are filled with a null value.

In each frame F, the even bytes Byte 0, Byte 2, ..., Byte 20, Byte 22 are used for carrying a synchronization pattern SYNC1 , SYNC2, ... SYNC22. This pattern is split into twelve segments respectively inserted into twelve separate fixed fields: Byte 0, Byte2_; ..., Byte 22. that are interleaved with the twelve fixed fields Byte 1 , Byte 3 Byte 23 that respectively contain the twelve respective values of the twelve ECG signals,

This synchronization pattern is distributed along a major part of the frame F. This distribution provides a quicker and more stable synchronization than a pattern comprising a single field of 96 bits placed at the beginning of each frame,

According to a preferred embodiment, the fields Byte 0, Byte2, ... , Byte 22 dedicated to the synchronization pattern segments SYNC1 , SYNC2, ... SYNC22, respectively contain a series of twelve incremented values T T^ 2, 3, 4, ,.., 12, that are coded with four bits. This synchronization pattern 1 , 2, 3, 4, .. , 12, is easy to generate with a counter in the sampling unit SU: and it is easy to detect by correlation with a counter in the restoration unit RU,

An EGC signals is commonly called a "lead". The 12 leads of a standardized EGC are divided up as follows:

• I, II, III are Standard Limb Leads t aVR, aVL, aVF are Augmented Limb Leads

• V1 ₍ V2, V3, V4, V5, V6 are Chest Leads Each of the incremented value can be used, by the restoration unit RU, as a signal identifier since:

- the value of signal D1 , corresponding to lead I, is placed, in the frame F, just after the synchronization pattern segment SYNC4- that has a value 1 ,

- the value of signal D2, corresponding to lead II, is placed, in the frame F, just after the synchronization pattern segment SVNC4- that has a value 2,

• the value of signal D3, corresponding to lead III, is placed, in the frame F, just after the synchronization pattern segment SYNC4- that has a value 3,

• the value of signal D4, corresponding to lead aVR, is placed, in the frame F, just after the synchronization pattern segment SYNC that has a value 4,

^■ the value of signal D12, corresponding to lead V6, is placed, in the frame F, just after the synchronization pattern segment SYNC4- that has a value 12.

The four remaining bits in each of the even bytes are preferably used for transmitting a contact quality indication. An electrode may have a bad contact with the patient's skin: The electrode may be dry, the wire of the electrode may be disconnected, or some hair ^~may separate the^~electrode from the skin, The transmission unit monitors the contact quality by monitoring the amplitude of the ECG signals, or by another known method. It is advantageous for the user that the transmission unit gives a warning when it detects an abnormal contact. For instance, one bit indicates Good Contact 'Bad Contact for each electrode EGC signal, and it is easy to determine the concerned electrode.

Three other bits remain available in each even byte: Byte O, ..., Byte 22, for signals supplied by other sensors.

Other bytes: Byte 24 Byte 29 are used for time-stamping each ECG signal sample, i e. associating the real time of the signal capture. The real time is provided by a real time clock embedded in the transmission unit 1 :

- Byte 24 carries a year indication,

- Byte 25 carries a month indication, - Byte 26 carries a day indication,

■ Byte 27 carries an hour indication,

- Byte 28 carries a minute indication,

^■ Byte 29 carries a second indication. In addition: - Byte 30 carries a battery status: Battery OK/ Battery Low,

^■ Byte 31 can be assigned to any other supplementary information, for instance an alarm signal if the transmission unit 1 detects that the patient is in danger, by detecting an abnormality in the ECG signals.

According to a second embodiment, each of the twelve EGC signals is linearly digitized on 12 bits carried in a field constituted by two successive bytes. The frame has still 32 bytes. Four remaining bits of each even byte, β/te 0,..., Byte 22 are then used for the synchronization pattern. Twetve contact quality indications may De transmitted in four ^"bits ^"of the^~b/te^~s Byte 30, Byte 31

According to another embodiment, the real time of the signal acquisition is inserted into only one frame sent at the beginning, or at the end, of the transmission. This is enough for short ECG recordings that generally last 35 seconds. The available bits can be used to carry:

^■ An indication about the number of electrodes really used, since an ECG may be made with a number of electrodes lower than twelve-ten. ■ An indication of the leads configuration. Sometime, non standard leads are used, these non standard leads are commonly identified as Right Precordial ιV4R, V5R, V6R) and posterior leads (V7, V8, V9).

- The sampling rate, because it can set to a value different of 250 Hz.

■ An accurate indication of the battery status: its voltage, or a percentage representing its charge, or an estimated availability time, or a number of samples that can be still be acquired before exhaustion of the battery,

- An index that can be placed by the patient when pushing a button on the transmission device, to accurately indicate when he/she feels some pain, palpitations, or some other abnormality in his 'her heart beat.

Claims

THERE IS CLAIMED:

1 > A wireless transmission method for at least N physiological signals characterized in that it comprises the steps of inserting N respective values of N physiological signals into N fixed fields (Byte 1 , Byte 3, ... , Byte 23 » of a fixed length frame (F), and then sending each frame (F) in a transmission channel (SCOL) adapted for transmitting a voice signal in a synchronous mode.

2 ) A wireless transmission method according to claim 1 , characterized in that said transmission channel (SCOL) is a synchronous connection oriented link (SCOL).

3 ) A wireless transmission method according to claim 2, characterized in that it further comprises the step of inserting in each frame (F) a synchronization pattern (SYNC1 , SYNC2, ... SYNC22) comprising N separate fixed fields (Byte O, Byte2, ... , Byte 22} that are interleaved with N fixed fields (Byte l , Byte 3, ... , Byte 23) that respectively contain the N respective values of N physiological signals.

A) A wireless transmission method according to claim 3, characterized in that said N separate fixed fields (Byte 0, Byte2. ... , Byte 22 ) of the synchronization pattern (SYNC1 , SYNC2, ... SYNC22 ) respectively contain a series of N incremented values.

5) A wireless transmission method according to claim 1 , characterized in that it further comprises the steps of inserting a real time indication into at least some of the transmitted frames.

6) A wireless transmission method according to claim 1 , characterized in that it further comprises the steps of inserting, into each frame (F), an indication of the real time of capture of the signals.

7) A wireless transmission method according to claim 2, characterized in that said synchronous connection oriented link (SCOL) is a Bluetooth link.

8) A wireless transmission device (1 ) for physiological signals characterized in that in that it comprises means (SU, BT) for inserting N respective values of N physiological signals into N fixed fields (Byte 0, Byte 2. ... , Byte 22) of a fixed length frame ( F), and means (BT) for sending each frame (F) in a transmission channel (SCOL) adapted for transmitting a voice signal or data in a circuit mode.

9) A wireless transmission device (1 ) according to claim δ characterized in that said means (BT) for sending each frame (F) are adapted for transmitting each frame in a synchronous connection oriented link (SCOL).

10) A wireless transmission device ( 1 ) according to claim 8 characterized in that it comprises means (SU, BT) for inserting in each frame (F) a synchronization pattern (SYNC1 , SYNC2, ... SYNC22) comprising N separate fixed fields (Byte 0, Byte2, ..., Byte 22 ) that are interleaved with N fixed fields < Byte 1 , Byte 3, ... , Byte 23 ) that respectively contain the N respective values of N physiological signals.

11 ) A wireless transmission device ( 1 ) according to claim 10 characterized in that said means (SU, BT) for inserting in each frame (F* a synchronization pattern (SYNCI , SYNC2. ... SYNC22 ) are adapted for inserting in a series of N incremented values respectιvely^~into^~saιd N separate fixed fields (Byte 0, Byte2, ..., Byte 22 » of the synchronization pattern (SYNC1 , SYNC2, ... SYNC22 I.

12) A reception device ( 3 ), characterized in that it comprises means (S) for receiving fixed length frames ( F) from a transmission channel (SCOL i adapted for transmitting a voice signal or data in a circuit mode, and means (RU) for extracting N respective values of N physiological signals, from N fixed fields (Byte 1 , Byte3, ..., Byte 23 » of a received frame (F) .

13 ) A reception device (3) according to claim 12, characterized in that said means (S i for receiving fixed length frames (F) are adapted to receive each frame from a Bluetooth synchronous connection oriented link (SCOL) .

14) A reception device (3) according to claim 12, characterized in that said means (RU) for extracting N respective values of N physiological signals are adapted to detect, in a frame (F), a synchronization pattern (SYNC1 ,

SYNC2 SYNC22 ) comprising N separate fixed fields (Byte 0, Byte2, ... ,

Byte 22) that are interleaved with N fixed fields (Byte 1 , Byte 3, ... , Byte 23 ) respectively containing N respective values of N physiological signals.

15 ) A reception device ( 3) according to claim 14, characterized in that said means (RU ) for extracting N respective values of N physiological signals are adapted to detect, in a frame (F), a synchronization pattern (SYNC1 , SYNC2, ... , SYNC22 ) comprising a series of N incremented values (SYNC1 , SYNC2, ... , SYNC22 ) respectively placed in N separate fixed fields (Byte 0,

Byte2 Byte 22 ) that are interleaved with N fixed fields (Byte 1 , Byte 3,

... , Byte 231 respectively containing N respective values of N physiological signals.