Note: Descriptions are shown in the official language in which they were submitted.
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This is a divisional of application Serial No. 2,405,861 filed Apri117, 2001.
WIRELESS SYSTEM PROTOCOL FOR TELEMETRY MONITORING
BACKGROUND OF THE INVENTION
A. Field of the Invention
This invention relates generally to the field of devices used to measure
electrical bio-potential signals generated by a human body, such as
electrocardiogram
(ECG), electroencephalogram (EEG) and electromyography (EMG) signals. More
particularly, the invention relates to a wireless signal acquisition system
and over the
lo air communications protocol that is used between a plurality of wireless,
remotely
programmable transceivers, each coupled to a conventional patch electrode, and
an
associated base unit. The base unit obtains a patient's ECG, EEG or EMG signal
from the wireless transceivers and supplies the signal to monitor unit for
display_ The
wireless conimunications protocol allows the base unit to remotely configure
and
manage the wireless transceivers, prior to and during data acquisition and
iransmission.
B. Statement of Related Art
Conventional ECG monitoring typically ' requires direct wired electrical
connections between electrodes that are attached to the body of the patient at
one end
and to an ECG monitor on the other end. Electric biapotentials are measured at
the
electrodes and signals are transformed via bipolar and unipolar leads inio an
electrocardiogram.
Conventional ECG apparatus for hospital bedside monitoring typically
requires up to ten wired electrodes. Each electrode is attached to the body of
the
patient, and has a wire, several feet or more in length, leading to an ECG
monitor.
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The lengthy wired electrodes of conventional ECG apparatus obstruct the
patient and
limit the patient's freedom of movement. They are also cumbersome for the
physician or assisting nurse.
Telemetry systems for wireless ECG monitoring for patients in hospitals
30 currently exist_ These systems are more expensive, intended for greater
range (higher
power), and do not totally eliminate the physical electrode wires attacbed to
the
patient. Instead of being connected to the monitor, the electrodes are each
wired to a
single transmitter box that is worn by the patient. Some telemetry systems
also may
not handle a 12 lead ECG (10 wires) because of the wiring that is required
between
35 the electrodes and the transmitter box. For example, the Spacelabs
Ultraview
Modular Digital Telemetry system can only handle a maximum of four leads (5
wires).
Wireless medical monitoring and diagnosis systems have been proposed in the
prior art. U.S. Patent 5,862,803 to Besson et 'al. describes a wireless
electrode/sensor
40 patch system with sensor, controller and transceiver electronics contained
in an
electrode patch assembly. U.S. Patents 5,307,818, 5,168,814 and 4,981,141, all
issued to Segalowitz, describe a wireless electrode system for ECG monitoring.
The
Segalowitz patents describe a single piece electrode patch with built-in
microchips for
45 wireless one way communication, and a snap on electronic-assembly that
fastens to a
disposable electrode patch. However, the electrode patch is a special two-
conductor
type that is not conventional. The electrode assemblies are either transmit
only or
receive only (not both). A reference signal (generated from a Wilson network)
is
transmitted from the base unit to only the Right Leg electrode patch, which is
receive
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5o only. Electrodes can only be programmed via manual switches on the
electrode
casing, not over-the-air from the base unit. For the multiple electrode
embodiment,
the base unit contains multiple receivers and antennas which imply multiple
transmit
frequencies are required for the system a nd over-the-air signaling (thus
making the
base unit more costly to implement). There is no mention of en:or correction
or 55 detection capability in the electrodes or base unit:
In another embodiment of the Segalowitz '818 patent, there is discussion of a
single strip assembly which contains all of the electrodes required for 12-
lead ECG
monitoring with microchip circuitry contained in the strip assembly (not in
the
individual -electrode patches). In this configuration, the ECG signals from
each
60 electrode are multiplexed and transmitted from a single transmitter
(contained in the
strip assembly) via time multiplexing on a single digitally encoded frequency
channel.
However, no time multiplexing on a single frequency channel is discussed for
their
multiple transmit electrode embodiment:
The purpose of the invention is to define a communication protocol, i.e., set
of
65 command procedures, for a wireless (leadless) electrode system that
replaces the
physical wires between the electrodes attached to the patent and the
monitoring
system base unit. The definition of communication protocols or procedures for
programming the electrodes over-the air is necessary to provide flexibility in
cotifiguring the wireless electrode system to the variable environmental
conditions
70 that exist across a wide scope of patent population, as well asdifferent
application
area or needs. The wireless system allows the patient a greater degree of
mobility
within the neighboring area- without wony about accidentally disconnecting the
electrodes or being disconnected from the monitoring equipment. A wireless
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monitoring system also provides better patient safety since the patient is
electrically isolated
from the monitor. This monitoring system is also more immune to noise
artifacts since the
digitization process of the data occurs right at the electrode measurement
point and not
through extended wires. The protocol defined herein describes initialization,
configuration
and management of the wireless electrode network. It also describes data
acquisition and
transfer to the base unit that synchronizes and coordinates electrode
functions.
SUMMARY
In accordance with the invention of this divisional application there is
provided a machine-
readable storage medium containing a set of instructions executable in a base
unit for over-
the air programming of a plurality of wireless transceivers, each of the
wireless transceivers
being adapted to couple to a sensor for connection to a patient's body. The
set of instructions
generates commands for remotely configuring and managing the acquisition of
physiologic
signals from the patient's body and transmission of the physiologic signals
from the wireless
transceivers to the base unit in real time either prior to or during a period
in which the
physiologic signals are being acquired. The commands from the base unit and
responses to
the commands from the wireless transceivers are operable to assign anatomical
positions to
be used by each of the sensors. The wireless transceivers preferably contain a
set of
instructions for responding to the commands.
The set of instructions may prompt the base unit to generate a set of
registration
commands and/or signal loss recovery commands and/or to configure the data
transmission
properties of the wireless transceivers and the wireless transceivers may
contain a set of
instructions for responding to the set of registration instructions and/or
signal loss recovery
commands. The data transmission properties may include selection of a carrier
frequency
and a time slot in a time division multiplexing communication format and/or
selection of
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communication parameters in a code division multiple access communication
format.
Further, the set of instructions may include a base unit configuration routine
wherein the
base unit programs patient identification and position location information
into the wireless
transceiver assembly. The set of instructions may also include a sensor
initialization routine
and/or a sensor activation routine and/or a sensor data acquisition subsystem
configuration
routine.
Another aspect ofthe invention provides an improved wireless system for
medical
monitoring having a base unit and a plurality of wireless sensors for
attachment to a patient's
body. In accordance with the invention, each of the wireless sensors has a
transceiver
assembly for transmitting and receiving two-way wireless communications with a
base unit.
The transceiver assembly includes a computing platform (such as a
microcontroller) and a
memory storing a set of instructions for execution by the computing platform
in response
to commands received from the base unit.
The base unit is provided with a wireless transceiver for transmitting and
receiving wireless communications with the sensors. The wireless
communications include,
among other things, commands for the transceiver assemblies. Further, a set of
instructions
is provided in the base unit, such as in a memory for a base unit
microcontroller, wherein
the base unit issues the commands to the transceiver assemblies in response to
the execution
of the instructions. The commands from the base unit and the responses to
those commands
from the transceiver assemblies comprise a procedure or protocol by which the
base unit
may remotely, and
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automatically, manage and configure the transceiver assemblies during real
time as
the transceiver assemblies acquire and transmit physiologic signal data to the
base
10o unit.
The wireless communications procedures described herein are particularly
well suited for use in a system acquiring EEG, ECG or EMG signals from a human
patient. The programmable wireless transceivers are associated with a sensor
in the
form of a conventional patch electrode, and acquire bio-potential signals
between
1os conductors in the electrode. The patch electrodes are of conventional
design and
adapted to be placed on the surface of the patient's body for measuring
electrical bio-
potentials.
A robust wireless monitoring system needs to allow ease of configuration and
calibration due to the variability of physiology acrnss patient populations.
The
110 present invention describes wireless programming procedures that allow
flexibility in
configuration of telemetry based electrode system to adapt to changing
requirements
of different applications. This invention provides for procedures that are not
only
specific to ECG, but can equivalently be applied in other application areas
such as
EEG, EMG, EOG, Respiratory, Tonometric Blood Pressure, Temperature and other
115 wireless medical monitoring systems. Furthermore, the programming
procedures are
dynamic, responsive to real time conditions as data is being acquired and
transmitted
to the base unit.
The protocol provides for transmission of a variety of configuration
commands. Examples of such commands include registration information, data
120 acquisition control commands (such as start and stop messages),
transmission
frequency commands, time slot commands, amplifier gain commands, transmitter
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control conimands, power saving mode commands, initialization commands, and so
forth.
The ability to remotely program the wireless transceivers gives considerable
125 tlexibility over how the electrodes -are configured and positioned on the
patient's
bocly. The programmable wireless transceivers could be designed to be
installed on
particular locations of the patient's body, such as left anm, right ann, left
leg, etc. In
a more preferred embodiment, the remotely programmable electrode transceivers
are
generic with respect to particular placement locations on the surface of a
patient's"
13o body. The base unit transmits programming data to the individual wireless
transceivers. The programming data includes electrode position location data
associated with a unique placement position to be assigned to the individual
wireless
transceivers, as well as electrode identification data. When the data is
acquired from
each of the wireless transceivers, the electrode identification data,
electrode position
135 location data and the acquired electrode signal are sent from the wireless
transceivers
to the base unit.
The base unit and the wireless transceivers may use time division multiplexing
as a communications format for transfer of the acquired signals to the base
unit. In
this case, the base unit transmits a global time base signal to the plurality
of individual
140 wireless transceivers. The global time base signal is used for
synchronizing the
timing of transmission of signals acquired by the individual wireless
transceivers to
the base unit in discrete time slots in a single frequency channel. This time
division
multiplexing provides that each wireless transceiver transmits its signals to
the base
unit in discrete time slots, with the wireless transceivers sharing a common
frequency
145 channel.
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These and still other aspects and features of the invention will be more
apparent from the following detailed description of a presently preferred
embodiment.
In this specification, the terms 'wvireless transceiver" and "programmable
wireless transceiver" are meant to refer.to the wireless electrode transceiver
assembly
t 5o as a unit, as distinguished from the actual transceiver module within the
assenibly,
unless the context clearly indicates otherwise. Further, the use of the tenn
"electrode" is meant to be interpreted broadly to cover bio-sensors generally.
BRIEF DESCRIPTION OF THE DRAWINGS '
155 A presently preferred embodiment of the invention is described below in
conjunction with the appended drawing figures, wherein like reference numerals
refer
to like elements in the various views, and in which:
FIG. I is a schematic representation of the system of the present invention in
use with a patient to acquire ECG signals from the patient and supply them to
a ECG
160 monitor; .
FIG. 2 is a=detailed perspective view of one of the patch electrodes and
associated remotely programmable wireless transceiver of FIG. 1, it being
understood
that all of such. patch electrodes and wireless transceivers of FIG. I are of
a
construction similar to that shown in FIG. 2;
165 FIG. 3 is a block diagram of the wireless.transceiver assembly of FIG. 2;
FIG. 4 is a block diagram of the base unit of FIG. 1;
FIG. 5 is a diagram illustrating the time division multiplexing of
transmission
fonnat for the plurality of wireless transceivers of FIG. I in the uplink
direction (the
direction of wireless transmission from the wireless transceivers to the base
unit), and
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170 the transmission of synchronization, reference and control data from the
base unit to
the wireless transceivers in a common channel in the downlink direction;
FIG. 6 is a flow diagram illustrating a base unit initialization routine;
FIG. 7 is a flow diagram illustrating a wireless transceiver initialization
routine;
175 FIG. 8 is a flow diagram of a programming procedure for programming the
wireless transceivers of FIG. 1 when initializing the ECG system of FIG. 1;
FIG. 9 is a perspective view of a base unit of FIG. 4 and a group of wireless
transceivers being initialized according to the procedure of FIG. 8; and
FIG. 10 is a perspective view of three wireless transmitters after the
procedure
180 of FIG. 8 has been completed;
FIGs. 11-26 are illustration of the message flow between the base unit and the
electrode assemblies during various different programming procedures according
to a
preferred embodiment of the invention;
FIG. 27 is an illustration of a registration procedure by which the base unit
is
185 registered with the electrode assemblies;
FIG. 28 is an illustration of a signal loss and error recovery procedure
implemented by the base unit in the event of a loss of signal from orie of the
electrode
assemblies of FIG. 1;
FIG. 29 is an illustration of a monitoring configuration procedure;
190 FIG. 30 is an illustration of a monitoring start procedure;
FIG. 31 is a logic diagram representing a state machine and software modules
in the wireless electrode transceiver assemblies;
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FIG. 32 is a logic diagram representing a state machine and software modules
in the base unit;
195 FIG. 33 is a diagram of a electrode initialization with reset connection
routine
shown in FIG. 32;
FIG. 34 is a diagram of an electrode activation routine shown in FIG. 32; and
FIG. 35 is a diagram of electrode data acquisition and transmission control
routines of Fig. 32.
200
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention can be used in a system consisting of multiple smart
wireless transceiver devices sized to snap onto conventional disposable patch
wireless
sensors or electrodes for wireless patient monitoring, and a base unit
communicating
205 with the wireless transceivers that is also capable of interfacing to
existing
conventional bedside monitoring equipment, such as a standard ECG or EEG
monitor.
The wireless transceivers receive commands from the base unit such as
registration
information, transmission frequency commands, amplifier gain commands,
transmitter control commands, power saving mode, etc. and include hardware and
210 soflware or finmware for processing these commands and responsively
configuring
the wireless transceiver accordingly. These commands are the result of
execution of
program instructions in a computing platform, such as a microcontroller, in
the base
unit and a set of response instructions in a computing platform in the
wireless
transceivers. .
215 A global time base signal is transmitted from the base unit to the
electrodes to
serve in synchronizing the timing of acquisition of sample points for all
electrodes
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used in measuring input body surface potentials (e.g., ECG signal). In the ECG
example, the base unit receives the transmitted ECG signal from each electrode
(at
predetennined time intervals if time division multiplexing is the embodiment
of the
220 communication protocol), demodulates, decodes (with error correction),
digitally .
processes the data, applies any needed signal conditioning (amplification,
filtering),
and converts back to analog form for outputting the ECG signals to the
standard ECG
equipment for display. The base unit also has a universal interface to
existing .
standard ECG equipment so that the wireless link between the electrodes and
base
225 unit appears transparent to. the ECG equipment. The ECG equipment will
accept the
individual electrode signals for developing any required lead configuration.
The wireless transceivers and base unit use a unique over-the-air
communication protocol between the base unit and the electrodes which allows
wireless programming (configuration), identification, auditing, data
acquisition
230 control, and.transmitter control of each electrode used in the system
during real time.
For frequency bandwidth efficiency of the invention, the system could be
designed
sucli that transmission of multi-channel signals is on a single digitally
encoded
frequency channel between the base unit transceiver and multiple electrode
devices by
using time division multiplexing. For example, each electrode will receive
235 synchronization data from* the base unit on the same receive frequency,
and
instruction on which time slot to transmit it's digitally encoded data. This
makes it
possible for multiple patients each on a separate frequency channel to use the
wireless
system in the same hospital room if there is limited bandwidth.
Refening now to FIG. 1, a system 10 according to a presently preferred
240 embodiment is shown schematically for use with a patient 12. The system 10
10"
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acquires ECG, EMG, EEG or other types of signals from the patient 12 and
supplies
them to a monitor 14. The present example will be discussed in terms of an ECG
system, but the invention is directly applicable to other types of inedical
monitoring.
The system 10 is a wireless system, in that a plurality of electrode
assemblies
245 16 receive commands (e.g., synchronization and control 'commands) from a
base unit
18 using wireless transmission methods, and supply the ECG signals to the base
unit
18 using wireless transmission methods as well. Thus, cumbersome wires for the
electrode assemblies 16 are eliminated in the illustrated embodiment.
The electrode assemblies 16 of FIG. I consist of a plurality of individual,
250 remotely programmable wireless transceiver assemblies 20, each transceiver
assembly
designed to snap onto a conventional patch electrode 22 (such as the 3M Red
dot
electrode) used in ECG monitoring. The wireless transceivers 20 are described
in
fi,rther detail in conjunction with Figure 2 and 3. The base unit 18 includes
a wireless
transceiver for sending and receiving messages to the plurality of individual
wireless
255 transceivers, and is described in further detail in conjunction with
Figures 4, 6, 8 and
9. The base unit further has an interface for providing analog ECG signals
received
from the wireless transceivers 20 to a conventional ECG display monitor 14.
A preferred conzmunications format for wireless communication between the
base unit 18 and the wireless transceivers 20 is time division multiplexing in
a
260 common frequency channel in the uplink direction, that is between the
transceivers
and the base unit. Each wireless transceiver 20 transmits ECG signals in a
particular
time slot in the channel, as indicated in FIG. 5. In the downlink direction,
the base
unit transmits control commands and other infonnafion in a common channel that
all
the wireless transceivers are tuned to. The time slot assignment, frequency
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265 assignment, and other transmission control information is managed and
controlled by
the base unit 18, as described in further detail below. An alternative
embodiment is
to use code division multiple access (CDMA) communication format for wireless
communication between the base unit 18 and the wireless transceivers 20.
The messages transmitted by the base unit 18 also include configuration
270 commands for the wireless transceivers 20. These configuration commands
can be,
for example, change or set the data acquisition sampling rate, amplifier gain
setting,
and channel carrier settings, and can also consist of a timing signal for
synchronization of the transmission time slot. Preferably, the base unit 18
transmits a
global time base signal to all of the wireless transceivers. The global time
base signal
275 synchronizes the timing of transmission of the ECG signals acquired by all
of the
wireless transceivers 20, such that the transmissions are in discrete time
slots in a
single frequency channel, as shown in FIG. 5.
The details of the over-the-air programming protocol to excbange messages
and information between the base unit and the transceivers may be arrived at
in many
280 ways within the spirit of the present invention, and is considered within
the ability of
a person skilled in the pertinent art from the present disclosure. In one
possible
embodiment, packets of data are transmitted between the base unit and the
wireless
transceivers. Particular fields in the packets (bytes of data) are reserved
for control
data, payload data, CRC or error correction data, etc. in accordance with
known
285 wireless transmission protocols, conventional data transmission techniques
such as 1P
or Ethernet, or similar techniques. A presently preferred protocol and message
structure is described later in this document in conjunction with FIGs. 11-30.
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FIG. 2 is a detailed perspective view of one of the patch electrodes 22 or
sensors and associated remotely programmable wireless transceiver 20 assembly
16 of
29o FIG. 1, it being understood that all of such patch electrodes and wireless
transceivers
of FIG. 1 are of a construction similar to that shown in FIG. 2. The patch
electrode
22 is adhered to the surface of the patient's body 12 -in conventional
fashion. The
patch electrode 22 includes a conductor 24 supplying ECG or other signals to a
pin
26. The pin 26 is received in complementary pin receiving structure 28 in the
295 - wireless transceiver 20 so as engage (as in a snap fit) the two parts 20
and 22.
The pin receiving structure 28 conducts electrical impulses with respect to a
local ground reference to electronic circuitry in the wireless transceiver 20.
The local
ground reference consists of a flexible strip 21 connected to the transceiver
20 having
a tip or skin contact 21A, made from a conductive material, which is placed
300 underneath the patch electrode 22 in contact with the skin. The purpose is
to allow
the transceiver to measure the bio-potential difference between the signal
contact
point 26 and the local ground reference 21/21A. The material used for the
strip 21
could be a thin flexible material such as plastic with an intemal conductive
trace or
lead wire from the transceiver 20 to the skin contact point 21A. The skin
contact
305 point 21 A is preferably coated with conductive silver chloride (AgCI)
materia121 B on
one side thereof.
FIG. 3 is a block diagram of the wireless transceiver of FIG.s 1 and 2. The
transceiver assembly 20 snaps onto the post pin 26 of a disposable
conventional patch
electrode. Electrical signals provided from the electrode 22 are supplied to a
low
310 noise, variable gain amplifier 30 in the wireless transceiver 20. The
amplifier 30 may
include a pre-amp stage. The analog signal is filtered, sampled and converted
to
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digital signals in the A/D converter 32. The digital signals are supplied to a
computing platform, illustrated as a microcontroller/Digital Signal Processor
34. The
microcontroller performs signal processing of the digital signal supplied by
the A/D
315 converter 32. The signal processing functions include noise filtering and
gain control
of the digital ECG signal. In an alternative but less-preferred embodiment,
gain
control in the transceiver assembly could be performed by adjustment of the
amplifier
30 gain in the analog signal path. The microcontroller also processes commands
and
messages received from the base unit, and executes finnware instructions
stored in a
320 memory 36. The memory further stores a unique electrode identifier as
described in
fiirther detail below. The memory may also store a position location
identifier or data
associated with a position the electrode is attached to the patient. The
position
location identifier or data is dynamically programmable from the base unit.
The processed digital ECG signals are buffered in a buffer 38, supplied to an
325 encoder/decoder 40 and fed to a RF transceiver module 42 for transmission
to the
base unit via a low power built-in RF antenna 44. The transceiver 42 includes
a
modulator/demodulator, transmitter, power amp, receiver, filters and an
antenna
switch. A frequency generator 46 generates a carrier frequency for the RF
transmission. The frequency is adjustable by the microcontroller 34. A battery
45
330 with a negative terminal connected to a local ground reference provides DC
power to
the components. The microcontroller/DSP 34 controls the frequency generator 46
so
as to select a frequency for wireless transmission of data and control
messages to the
base unit. The microcontroller in the computing platform 34 also executes an
initialization routine wherein the receiver scans a default receive channel
for
335 commands from the base unit, and if the corrimands are received the
transmitter
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transmits identification information in an assigned frequency and time slot to
the base
ttnit.
All or some of the individual blocks shown in FIG. 3 could be combined in a
microchip or microchips to miniaturize the size of the snap-on wireless
transceiver
340 assembly 20.
Referring now to FIG. 4, the base unit 18 is shown also in block diagram form.
The base unit 18 transmits commands to all of the wireless transceivers and
instructs
each transceiver to transmit its ECG data individually (such as in = time
division
multiplexing). The base unit receives the transmitted ECG signals from the
electrodes
345 (up to .10) in sequence and then demodulates, decodes, error corrects, de-
multiplexes,
buffers, signal conditions, and reconverts each electrode's data back to an
analog
signal for interfacing to the standard ECG monitor 14. The base unit also
transmits
programming information to the electrodes for frequency selection, power
control,
etc.
350 The base unit 18 includes a low power RF antenna 50, a frequency generator
52 for generating a carrier frequency and an RF transceiver 54. The
transceiver 54
includes a modulator/demodulator, transmitter, power amp, receiver, filters
and an
antenna switch. The base unit further includes a encoder/decoder 56, a
computing
platform such as a microcontroller/Digital Signal Processor (DSP) 58, and a
memory
3s5 60 storing code for execution by the microcontroller/DSP, and I!O
interface 59 for
connection to a personal computer which is used as a test port for running
system
diagnostics, base unit software upgrades, etc., and a user interface 61. The
user
interface 61 may consist of the following: a display, for indicating electrode
programming information or error/alarm conditions, a keypad or buttons for
user
,~ .
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36o requested inputs, an alarm unit for audibly indicating error/alarm
conditions (for
example a detached, low battery or failed electrode), and LEDs for visually
indicating
error, alarm or programming status.
The time slot ECG data received from the wireless transceivers is
demultiplexed in demultiplexer 62 and supplied to a buffer 64. A digital to
analog
365 filter bank 66 converts the multiple channels of digital data from the
wireless
transceivers to analog form. The analog signals are amplified by amplifiers 68
and
supplied to an OEM (original equipment manufacturer) standard ECG monitor
interface 70. The interface 70 could be either part of the base unit 18
assembly so that
it can directly plug into the ECG display equipment 14 via a standard
connector, or it=.
370 could be part of a cable connection to the display equipment. The -idea
with the OEM
interface 70 is to supply multiple analog ECG signals to the conventional ECG
display equipment already used in the hospital environment, in a compatible
and
transparent manner, such that the display equipment would treat the signals as
if they
were generated from conventional wired electrodes. Familiarity with the-
analog
375 signal acquisition hardware or electronics for the ECG display equipment
14 will be
required obviously, and the OEM interface circuitry may vary depending on the
manufacturer of the display equipment. The OEM monitor interface detailed
design
is considered within the ability of a person skilled in the art.
Referring to FIG. 5, a possible transmission scheme between the wireless
380 transceivers 20 and the base unit 18 is time division multiplexing. This
allows a
single transmit frequency to be used by all the electrodes in the ECG system.
All
electrodes receive commands and synchronization data (time base signal,
reference
signal and control data 76) from the base unit 18 on an assigned receive
frequency
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(downlink) channel. The electrode receive channel may or may not be slotted
(time
385 multiplexed). Electrode 1 20/22A transmits it's data on time slot 1 72
(Electrode 2
20/22B on time slot 2 74, etc.) at the assigned transmit frequency (uplink)
channel.
The base unit 18 receives the transmission from the electrodes 20/22 and
demultiplexes, buffers, and reconstructs the individual electrode data.
The system 10 of FIG. I utilizes an over the air programming mechanism to
39o exchange messaging and information between the base unit 18 and the
wireless
transceivers 20. Various types of information could be exchanged. For example,
the
base unit 18 transmits a data acquisition control message to the wireless
transceivers,
which tells the microcontroller in the wireless transceivers to start and stop
data
acquisition. Another command would be a frequency selection command message(s)
395 sent to the wireless transceivers, in which the wireless transceivers
responsively select
a common frequency channel for transmission of acquired ECG signals to the
base
unit in discrete time slots.
The following is a list of some of the possible programming commands and
messages that could be sent between the base unit and the wireless
transceivers:
400 a. Registration of electrodes 20/22 with the base unit 18. This would
include the
detection of the electrode type and an associated unique electrode identifier
by the
base unit. This could also include transmission of a unique base unit
identifier to
the electrodes (for example where multiple base units are within RF range of
the
electrodes) and detection of the base unit identifier by the electrode. Also,
a
405 patient reference number could also be stored in each electrode so it only
receives
commands from a specific patient-assigned base unit. Each electrode reference
number is also stored in the base unit, so that data coming only from these
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electrodes is accepted. An additional registration feature would be assignment
of
a specific electrode function (i.e., position on the patient's body). This is
410 discussed in more detail below. With each of the above commands and
messages, the receiving unit would typically transmit back a response message
indicating the receipt of the command and sending back any required
information
to the transmitting unit.
b. Configuration of data acquisition sampling rate.
415 c. Configuration of amplifier 30 gain setting.
d. Configuration of preamplifier filter band settings.
e. Configuration of carrier channel settings, namely the frequency of the
carrier
signal generated by the frequency generator 46 in the transceivers.
f. Configuration of timing signal for transmission time slot. This needs to be
420 synchronized with the data acquisition rate.
g. Battery 45 utilization sleep/activation mode.
li. Battery 451ow voltage level detection. i. Data acquisition start/stop
scenario.
j. Data transmit procedure.
425 k. Error sample data recover/retransmit scenario.
1. System test diagnostic procedure
m. Scan of electrode current channel setting procedure
n. Electrode detection procedure.
o. Electrode status audit.
430 p. Base unit status audit
q. Data acquisition subsystem audit.
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Electrode unigue identifier:
The system 10 of FIG. 1 provides a registration mechanism for every
~V; wireless transceiver and electrode assembly whereby an electrode
identifier is
programmed into the base unit, as well as the electrode functional position on
the
patient (i.e., LA, RA, LL, V1, V2, V3, V4, V5, or V6 in an ECG embodiment). An
Electrode Serial Identifier (ESI) will encode the wireless transceiver's
unique serial
number. Each wireless transceiver is assigned an Electrode Temporary
Identifier
4,1 o (ETI) after each registration scenario (on power up or reconfiguration).
The
temporary identifier can be composed of electrode number and random number for
exainple. The ESI will be included in each message or data transaction from
each
electrode to the base unit. The electrode identifier will serve to ensure that
only
registered electrodes input signaling will be accepted by the associated base
unit, in
4-1 ~, ttie event that two monitoring systems are transmitting on the same
frequency
channel, or in the case of interference detection.
Base unit uniQue identifier
The system will provide a registration mechanism whereby a base unit
i(lentitier is programmed into the wireless transceiver assemblies being used.
The
V) o Base Unit Serial Identifier (BUSI) will encode the base unit serial
number. During
power-up or reconfiguration, a Base Unit Temporary Identifier (BUTf) is
assigned
ancl registered with the wireless transceiver assemblies. The base unit
identifier
will he included in each message or data transaction from the base unit to
each
wireless transceiver assembly. The base unit identifier will serve to ensure
that
4 55 only the registered base unit input signaling (commands) will be accepted
by the
assemblies, in
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111, event that two monitoring systems are transmitting on the same frequency
ci,...;mel, or in the case of interference detection.
460 Electrode Svstem Initialization
Figure 6 shows a flow diagram of a possible initialization procedure (for both
the base unit 18 and electrodes 20/22) for use where the transmission scheme
between
the base unit and the wireless transceivers 20 is time division multiplexing.
This
procedure assumes that each electrode in the ECG-system contains a unique
identifier
465 and a unique functionaI position ID (i.e., LA, RA, LL, VI, V2, V3, V4, VS,
or V6).
The procedure of FIG. 6 is reduced to a set of instructions stored in the base
unit's
memory 60 for execution by the microcontroller 58, as shown in FIG. 4, and in
a set
of response instructions stored in the wireless transceiver 22's memory and
microcontroller of FIG. 3.
470 At step 80, the base unit is powered up. The base unit is configured for
the
number of leads used in the ECG system, such as 3, 5 or 12. The configuration
could
be facilitated by means of any suitable user interface on the base unit 18,
such as a
display and buttons as shown in FIG. 9 and described subsequently. At step 82,
the
base unit scans its receive channels, a list of which is programmed into the
base unit.
475 At step 84, the base unit determines whether any other ECG base unit
transmissions
are detected. If so, at step 86 the base unit selects the next unused
frequency from the
list of predetermined frequency channels as a transmit channel. If not, at
step 88 the
base unit selects the first frequency from the list ofpredetennined frequency
channels
as the transmission channel. The process then proceeds to step 90.
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480 At step 90, the base unit stars transmitting =electrode registration data
and
messages on the default programming channel determined in steps 86 or 88. The
registration data and messages include a base unit identification code or
serial
number. The registration data and messages were described earlier. This
insures that
the wireless transceivers to be associated with this particular base unit
being
485 initialized respond to commands from this base unit and no other base
unit. At step
92, the base unit instructs all required electrodes to transmit on a
predetermined
frequency channel, and assigns time slots to each electrode. The base unit
then
communicates with electrodes to complete registration. If a particular
electrode or
electrodes did not complete registration, the base unit indicates via its user
interface
490 which electrode is not registered at step 96. If registration is completed
for all the
electrodes, the base units instruct all electrodes to receive commands on a
new
predetermined frequency channel at step 98. At step 100, the base unit
instructs all
electrodes to begin ECG data acquisition and to transmit at the assigned
frequency
and in the assigned time slot. Step 100 may be started in response to a user
prompt
495 via the base unit user interface. During data acquisition, at step 102 the
base unit
continuously monitors for interference on the receive data channel (uplink
direction).
If excessive interference occurs (such as from a high bit error rate detected
in the base
unit microcontroller), the base unit selects a new channel from the list of
available
frequencies for the electrodes to transmit on and commands a change in
transmit
500 frequency.
FIG. 7 is a flow diagram of an electrode initialization procedure that may be
employed. When the electrodes are initially powered up at step I 10, the
electrodes
will be in a receive only mode. At step 112, the electrodes automatically scan
the
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default receive channel to see if any commands and synchronization signals are
being
505 transmitted by the base unit. If no conunands and synchronization commands
are
received at step 114, the electrode goes back to step 112 and selects another
receive
frequency from its list of default frequencies. If commands and
synchronization data
liave been received, at step 116 the electrode sends is unique identification
data
(containing information on the position on the patient's body) on the assigned
510 frequency and in the assigned time slot back to the base unit, indicating
to the base
unit that it is ready to acquire ECG signals and is in an operating condition.
In an alternative embodiment of the invention, the plurality of individual,
remotely programmable wireless transceivers 20 are initially generic with
respect to
particular placement locations on the surface of a patient's body.
Furthermore, the
515 electrodes could be nianufactured without preprogrammed . functional
position
identifiers. This is advantageous since it would not be necessary to have the
hospital
or user maintain an inventory of individual electrodes based on functional
position
(i.e., LA, RA, LL, V 1, V2, etc.). All the electrode assemblies are considered
generic
and could be progranuned with unique identifiers indicating the position on
the body
52o by the base unit when the user sets up the ECG system. The procedure of
FIG. 8
could be used for programming of each electrode when initializing the ECG
system.
Afier first time programming of the electrode assemblies, the system only
needs to go
through the initialization program of FIG. 6 when it is powered up again.
FIG. 8 shows the initialization procedure in the altemative embodiment. FIG.
525 9 shows the base unit 18 having a user interface 61 comprising a display
132 and a
plurality of buttons or keys 133 for assisting the user to interact with the
base unit. A
group of generic wireless transceivers 20 are shown ready for initialization.
The user
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lias a set of pre-printed labels 135, which are removed from a plastic backing
and
placed on the wireless transceivers as shown in FIG. 10.
530 Referring now to FIG. 8 and 9, at step 140 the user sets up the base unit
into
an electrode programming mode, such as by responding to prompts on the display
132
and selecting the mode with one of the buttons or keys 133. The base unit
programming mode could be done at lower power transmissions, requiring the
wireless transceiver 20 to be programmed to be adjacent to the base unit
(thereby
535 avoiding programming more than one transceiver at a time). Alternatively,
as shown
in FIG. 9, the base unit has a programming initialization interface 136 which
makes
contact with a socket or other feature in the transceiver for purposes of
programrning
the transceiver during initialization. When the transceiver is placed into
contact with
the programming initialization interface 136, the base unit could
automatically=go into
540 programming mode, or it could simply go into programming mode upon power
up.
In any event, at step 142 the first electrode assembly 20/22 is powered up and
placed near the base unit or positioned in contact with the programming
initialization
interface 136. The initialization of the electrodes could be done by
mechanical
means, such as plugging the electrode transceiver 20 into the base unit
programming
545 initialization interface 136.
At step 144, the electrode scans the default programming channel. At step
146, the base unit sends a low power programming command on the'default
transmit
channel or some other channel that has the least RF interference. At step 148,
the
electrode determines whether it has received the programming command. If not,
the
550 electrode scans the list of default channels and -selects a new channel to
listen on. If
so, the electrode transmits a response message on its assigned transmit
channel at step
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150. At step 152, the base unit determines whether it has received the
response from
the electrode. If not, the base unit goes back to step 146 and transmits the
low power
programming command on a new transmit channel. If so, the base unit transmits
555 programming data to. the electrode at step 153. At step 153, the
programming data
includes the electrode unique identifier, including the electrode position
(LA, RL, or
V3, etc.), the base unit unique identifier, and other registration commands as
described above. At step 154, the electrode determines whether a programming
error
was detected, and if so at step 156 sends a retransmit program message to base
unit
560 causing it to repeat the programming data at step 152. If no error
occurred, the
process proceeds to step 158, at which the electrode completes programming
with the
base unit. At step 160, the base unit instructs the electrode to wait for
additional
commands. At this point, since the unique base unit ID has been programmed in
the
wireless transceiver, it can scan ECG system control channels and re.ceive and
operate
565 on commands only from the base unit that programmed the transceiver. At
step 162,
the base unit displays the electrode placement position on the user interface
display
and prompts the user to place the next electrode for programming into the
initialization interface 136.
After all the electrodes have been programmed, the base unit will
570 automatically be configured for the proper number of electrodes used in
the ECG
system. As each electrode is programmed the user removes a label 135 from the
stock of labels 137 indicating the position programmed on the electrode and
applies
the label to the electrode (e.g., to the top or upper surface of the wireless
transceiver
20), as shown in FIG. 10.
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575 From the foregoing description, it will appreciated that we have described
a
dynamically programmable, wireless electrocardiograph (ECG) acquisition
system,
comprising: a plurality of individual, remotely programmable wireless
transceivers
20, each transceiver associated with a patch electrode 22 for use in ECG
monitoring,
and a base unit 18 comprising a wireless transceiver 54 (FIG. 4) for sending
and
580 receiving messages to the plurality of individual transceivers 20. The
base unit and
wireless transceivers 22 implement a wireless programming protocol by which
messages and information are exchanged between base unit 18 and wireless
transceivers 20 (such as shown in FIG. 6 and 8) whereby registration,
configuration,
and data transmission control properties of the wireless transceivers may be
managed
585 by the base unit.
Preferably, the base unit transmits a global time base signal to the wireless
transceivers, the global time base signal synchronizing the timing of
transmission of
ECG signals acquired by the wireless transceivers in discrete time slots in a
single
frequency channel. As shown in FIG. I and= 4, the base unit further comprises
an
590 interface 70 to a conventional ECG monitoring equipment such as a display,
whereby
acquired ECG signals may be transmitted to the ECG monitoring equipment for
display. The system of base unit 18 and wireless remotely programmable
transceivers
20 is particularly well adapted for use with standard conventional patch
electrodes and
existing ECG monitoring equipment, and thus presents a flexible, low cost and
595 convenient approach to acquiring ECG signals and presenting them to a
display unit
for display.
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Over the air proPramminQ procedures:
600 The system 10 of FIG. 1 utilizes over the air (OTA) programming procedures
to exchange messaging and information between the base unit and electrodes
(that is,
the wireless transceivers 20). Various types of information could be
transacted for the
general purposes of registration, initialization, configuration, calibration,
data
acquisition control, transmission synchronization, error correction or
recovery, power
605 mode control, and auditing status.
The piogramming procedures described herein are based on a set of
instructions that are stored in a memory in the base unit (such as memory 64
of FIG.
4), and executed by a computing platform such as the microcontroller 58 to
generate
commands that are transmitted via wireless communication to the plurality of
wireless
610 electrodes. Similarly, the wireless transceivers in the electrodes receive
the
commands from the base unit, and execute instructions stored in a memory in
order to
respond to the commands and transmit response messages (such as audit response
messages etc.) back to the bast unit. The following is a description of these
instructions. Preferred embodiments of such procedures (i.e., sets of
instructions) are
615 described below in conjunction with FIGs. 11-30:
a. Conftguration of data acquisition sampling rate procedure. Variable
sampling data rates could be set to accommodate varying physiologic signals
(ECG, EMG, EEG, etc.). The sampling rates will differ according to the
nature of frequencies evoked in such physiologic events. Also, certain
620 application needs for specialized tests within a specific area may require
faster
sampling rates.
The programming procedure of FIG. 11 is employed to configure the
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-data acquisition sampling rate. The base unit 18 sends a data acquisition
configuration message 200 to the electrode assembly 16 (i.e., wireless
625 transceiver 20). The message contains data identifying a sampling rate for
the
wireless transceiver's A/D converter. When the message 200 is received by
the wireless transceiver and processed in the microcontroller, the sampIing
rate for the A/D converter is cbanged. The wireless transceiver sends back a
data acquisition configuration complete message 202 indicating that the
630 change is data sampling rate was accomplished.
b. Configuration of amplifier gain setting procedure. Variable signal pre=
amplification gain (prior to digitization) could be set to accommodate and
correct for weak bio-potential signal strength at the skin surface, or a bad
surface connection, as well as changes in skin resistance due to dry or humid
635 environmental conditions and temperature changes. The signal amplification
gain factor could be adjusted dynamically until a reasonable signal strength
is
obtained. Typically, ECG signals re in the 1-5 mV range, while EEG signals
are in the 1-100 V range. Different gain selection is desirable to obtain the
sensitivity that is needed for the specific application.
640 When the base unit determines that the amplifier gain needs to be
adjusted, the procedure of FIG. 12 is used. The base unit sends an amplifier
gain configuration message 204 to the electrode 16's wireless transceiver 20
(FIG. 3). The microcontroller 32 processes- the message and adjusts the gain
setting to the amplifier 30 providing an analog signal to the A/D converter 32
645 of FIG. 3. When the gain has been adjusted, the transceiver sends a gain
configuration complete message 206 back to the base unit.
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c. Configuration of pre-ainplifier ' (anti-aliasing) filter band settings
procedure. Flexibility of adaptation of the monitoring system 10 to variable
application needs may require a dynamic re-selection of an anti-aliasing
filter
650 band in the preamplifier of the wireless transceiver. An optimal filter
can be
selected from a bank of filters pre-set at different frequency bands to filter
out
noise or unwanted artifacts. The programming procedure of FIG. 13 is
employed. The base unit sends a set filter band message 208 identifying the
frequency band (or filter) for the anti-aliasing filter (not shown) in the
analog
655 signal path in the wireless transceiver.
d. Configuration of carrier channel setting procedure. In order to allow
multiple users of monitoring systems to co-exist in same physical area, and at
the same time reduce the possibility of interference, a multi-frequency
channel
system is implemented to eliminate the possibility of interference in
660 communications between the base unit 18 and the wireless transceivers of
any
given system 10. - The base unit 18 dynamically detects interference by
listening to a specific frequency channel during configuration, such as a
default frequency channel, and determines the suitability of use for the
monitoring system based on noise levels in that frequency channel. The base
665 unit 18 can also apply this procedure if too many errors were encountered
during the decoding of signaling received on a specific channel due to
increasing noise, or during system reset and reconfiguration procedures.
The procedure of FIG. 14 is employed for carrier channel setting
changes. The base unit sends a set carrier channel message 212 to the
670 electrode. The message 212 identifies the new carrier channel. The
wireless
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transceiver's frequency generatoi is responsively adjusted to generate a
carrier
signal at the new frequency. When the configuration is complete, the
electrode sends a carrier configuration complete message 214 back to the base
unit.
675 e. Configuration of timing signal for transmission time slot procedure.
The
procedure of FIG. 15 sets the assignment of a specific time slot for each
wireless transceiver (in a time division multiple access (TDMA)-based
system) for transmitting and/or receiving data between the electrode's
wireless
transceiver 20 and the base unit 18. Such synchronization is necessary in a
680 TDMA-based system to allow multiple electrodes transmitting on the same
frequency channel to relay their information to the base unit without
interfering with one another. The procedure consists of the base unit sending
a set time slot message 216 to the electrode, identifying a particular time
slot
for each electrode. When the electrode has set the time slot, it sends back a
685 time slot set complete message 218.
f. Battery utilization sleep/activation mode procedure. The battery
utilization
sleep mode procedure of FIG. 16 will be used during shut-down process for
conservation of battery power. This can also be initiated if signal
communication is lost between the electrodes and the base unit, or on
690 command from the base unit. Battery utilization activation mode will be
'initiated as soon as communication with the electrodes is resumed or during
initialization of registration of new electrodes. The proceduTe involves the
base unit sending a battery audit request message 220 to the electrode. The
message 220 basically asks the electrode to provide battery life and current
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6 9 5 battery mode information. This information is provided back to the base
unit
in a battery audit response message 222.
g. Battery low voltage level detection procedure. A battery status audit
procedure shown in FIG. 17 is for a condition of low battery voltage in the
wireless transceiver 20 to be detected by the base unit. The procedure
700 raIlows the base unit to warn the user for replacing or recharging that
electrode battery. When the voltage of battery 46 of FIG. 3 goes below a
threshold level (as monitored by the microcontroller), the electrode sends a
low battery detected message 224 to the base unit.
h. Power Saving Mode Setting. The procedure shown in FIG. 18 allows the
V W) b;ase unit to change the power saving mode of the wireless transceivers
to
conserve battery life and be more economical. Different levels of power
saving modes can be selected based on the needs of the operation. A
memory retention sleep mode can also be implemented in the wireless
transceiver. The system can also have a wake up timer or change to active
mode at the command of the base unit. The base unit sends a power saving
mode set command 226. The electrode responsively changes the state of
the battery 46 to a sleep or power saving mode, and when that is
accomplished sends back a power saving mode complete message 228
back to the base unit.
7 15 i. Acquisition start/stop procedure. The procedure of FIG. 19 allows the
base unit to command the electrodes to start the data acquisition and
transmit the data to the base unit, or stop the data acquisition process.
Multiple start/stop messages of the type shown in FIG. 19 may be needed
to interrupt a
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continuous data streaming of information to the base unit in the event of
720 reconfiguration, a frequency channel re-selection is needed due to
interference, or when power saving (sleep) mode is requested. Other
situations are possible. The procedure begins by the base unit sending a start
data acquisition message 230 to the electrodes. The electrodes acknowledge
the start of data acquisition with a acquisition started message 232. The base
725 unit then commands the electrode to start transmission of data by message
234. The data is sent from the electrodes as indicated by data transfer
messages 236. In this illustrated embodiment, this is by time division
multiplexing on a single carrier frequency in time slots and by frequency as
provided in FIGs. 14 and 15.
730 j. Data transmit procedure. Once data acquisition is started, data is
transmitted from each of the electrodes to the base unit in either a
synchronous
or an asynchronous manner. This is shown in FIG. 19. At the base unit, data
is decoded, collected, buffered, and checked for error occurrence during
transmission. Base unit 18 also controls the stoppage of data transmission, as
735 shown in FIG. 20. This procedure involves the base unit sending a stop
- acquisition message 238. The electrode ceases data acquisition and
transmission and sends an acquisition stopped message 240 back to the base
unit.
k. Error sample data recover/retransmit procedure. In the event of an error
740 occuning during transmission of the data from the electrodes to the base
unit,
the data can be requested for re-transniission. This procedure is shown in
FIG.
21. The base units sends a retransmit data message 242 to the electrode. In
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response, the electrode retransmits stored data stored in the memory 36, as
indicated at 244. The electrode should =have a ininimal buffer storage of the
745 previous data collected in"buffer 38 in the event error recovery is needed
due
to a noisy or bad signal transmission.
1. System test diagnostic procedure. The procedure of FIG. 22 instructs the
clectrodes to transmit a diagnostic test data pattern in order to analyze the
system for optimal performance. Also, it may be used 'to resolve issues in
750 local ground referencing across all electrodes for calibration purposes. A
diagnostic test initiate message 246 is sent from the base unit to the
electrode.
Receipt of the message 246 causes the microcontroller to initiate certain
tests
or transmit a diagnostic test pattern according to a set of instructions or
code
stored in the memory 68 designed to respond to the message 246. A test
755 initiated message 248 is ' sent back to the base unit, acknowledging the
message 246. After the test is performed, test data is transmitted to the base
unit as indicated at 250. When all of the test data has been received, the
base
unit sends a test complete message 252 to the electrode, and the message is
acknowledged by a test completed message 254.
760 m. Scan of electrode current channel setting procedure. A procedure may be
implemented to allow the base unit to scan for an electrode that is
transmitting
on an unknown frequency channel. Using a signal strength indicator, the
specific transmission channel can be= determined. The electrode can be
reconfigured to transmit on a new channel using the procedure of PIG. 14.
765 n. Electrode detection procedure. The procedure of FIG. 23 is initiated
periodically,.as a means of providing a continuous search and "keep-alive"
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signal. The electrode detection procedure involves a connection message 256
that is transmitted.from the base unit to the electrodes. The electrodes
respond
with a connection confirm message 258 which tells the base unit that the
770 electrode is "alive". If this electrode detection message 256 is not
received
periodically by the electrodes, then they stop data acquisition and move into
a
power saving mode. The signaling can be done on an interval basis (e.g.,
every 30 seconds) and on the last previously selected traffic channel.
o. Electrode Status Audit: A procedure shown in FIG. 24 allow the electrode
775 status to be audited by the base unit when needed to ensure proper
operating
conditions and configuration parameters. The procedure involves the base
unit sending an electrode audit request message 260. The electrode responds
to the audit message with an audit response message 262 indicating current
operating conditions and configuration parameters, e.g., gain setting,
780 preamplification filter band, reference signal, time slot, carrier
frequency, data
acquisition rate, serial number, etc.
p. Base Unit Audit. Referring to FIG. 25, a base unit's status can be audited
by
the electrodes when needed to ensure proper operating conditions and
configuration parameters. The electrodes send a base unit audit request
785 message 264 to the base unit and it responds with an audit message 266
indicating its current configuration parameters, such as channel frequency.
q. Data acquisition subsystem audit. Referring to FIG. 26, the data
acquisition subsystem in the wireless transeeivers, consisting of the
preamplifier, amplifier and D/A converter, can be individually audited for
790 proper operation status and configuration settings. The base unit sends a
data
33 .
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acquisition (DAQ) audit request message 268 to the electrode and the
information is provided in a DAQ audit response message 250.
System Operation Procedures:
a. Registration of electrodes with the base unit. A preferred registration
795 procedure includes (but is not limited to) detection of electrode type and
identifier. _
The,patient reference number and/or demographics can also be stored in each
electrode so they are associated uniquely with a specific patient. Assignment
of
electrode function (anatomical or functioriaI position) in this monitoring
system is
also performed. Assignment of any temporary identifiers to the electrodes can
800 also be performed. The registration, procedure can be initiated on a
dedicated
frequency control channel(s) for initialization. The registration procedures
of
FIG.s 6 and 8 are one possible embodiment of the registration procedure.
Another
possible embodiment in shown in FIG. 27. The base unit sends a connection
request message 272 to the electrodes. The electrodes reply with a connection
Aos confinm message 274. This is the procedure of FIG. 23 descnbed previously.
Then electrode audit messages 276 and 278 are exchanged, the procedure of FIG.
25. The base unit sends a n ID/Function allocation message 280 that assigns
the
electrode with a temporary ID and body position or function. The electrode
sends
an allocation complete message 282 in response to the allocation message 280.
A
810 base unit registration message 284 is sent to the electrode, registering
the
electrode with the base and conveying the base unit identification to the
electrode.
A base unit registration complete message 286 is sent in response. Messages
288, 300, 302 and 304 assign the time slot and carrier channel for the
electrode,
implementing the procedures of FIGs. 14 and 15.
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81s b. Registration of the base unit with the electrodes. A registration
procedure may
be implemented by which the base unit registers with the electrodes is also
performed. The procedure is shown in messages 284 and 286 of FIG. 27. The
procedure includes the detection of a base unit type and an identifier
associated
with the base.unit. The messages 284 and 286 of FIG. 27 serves to restrict
820 electrodes to accept communication from only a single base unit. The
registration
procedure can be initiated on a dedicated frequency channel(s) for
initialization.
c. Total signal loss recovery scenario. A procedure shown in FIG. 28 is
provided
which recovers from a total loss of signal from one or more of the electrodes.
The
procedure is initiated in the event of weakening transmission signal strength
due
825 to fading channels, or low available transmission power, or large physical
distance
between the electrodes and the base unit. A continuous search and "keep-alive"
signal is transmitted from the base unit to the electrodes. Once an electrode
is
detected, communication is re-established, and the base unit resumes
collection of
the data. The procedure begins with the cownection request and confirm
930 messages 306 and 308 (the procedure of FIG. 23 described previously), the
electrode audit messages 310 and 312 (the procedure of FIG. 24), and the data
acquisition subsystem audit messages 314 and 314 (the procedure of FIG. 26).
Depending on the response to the audit messages, the base unit may initiate
any
number of configuration commands to restore the electrode to a proper
operating
835 condition, such as the DAQ configure message 316 which configures the data
acquisition subsystem in the wireless transceiver. The electrode sends the
complete message 318 when the subsystem has been reconfigured in accordance
with the settings contained in the message 316. As another alternative, the
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carrier channel messages 320 and 322 can be exchariged (the procedure of FIG.
840 14). As another alternative; a diagnostic test can ba initiated as
indicated by
messages 324, 326, 328, 330, 332 and 334, implementing the procedure of FIG.
22 described above. Additionally, amplifier gain can be configured by messages
338 and 334 (the procedure of FIG. 12). Any or all of the messages shown in
dashed lines could be implemented. After a successful reconfiguration of the
845 electrode, data acquisition and transmission is reestablished by messages
340,
342, 344 and 346, namely the procedure of FIG. 19 described above.
d. Monitoring system conSguration scenario: A procedure shown in FIG. 29 is
provided for the overall monitoring system configuration. The system 10 will
set
up and configure multiple subsystems including: data acquisition, filtering
and
850 signal conditioning, amplifier gain setting, and rtm diagnostic tests to
ensure
quality of transmitted data. The configuration begins by a connection request
message and response connection confinn message 350 (the procedure of FIG.
23), the data acquisition subsystem audit messages 352 and 354 (the procedure
of
FIG. 26), the data acquisition subsystem configuration messages 356 and 358,
and
855 the setting of the preamplifier filter band by messages 360 and 362 (the
procedure
of FIG. 13). Then a diagnostic test procedure consisting of messages 362, 364,
366, 368, 370, 372, and 374 are exchanged, implementing the procedure of FIG.
22. An optional amplifier configuration command can be send as message 376
depending on the results of the diagnostic test just performed. When the
amplifier
860 gain is successfully changed 'the gain configuration complete message 378
is sent
back to the base unit.
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e. Monitoring system data acquisition start scenario: The system will start
the
data acquisition and transmission through the traffic channel to the base unit
once
865 system configuration is complete. The procedure of FIG. 30 shows one
possible
embodiment. A configuration request message 380 is sent, generating the
configuration confirm message 382 from the electrode (procedure of FIG. 23).
Data acquisition start messages 384 and 386 are exchanged (procedure of FIG.
19). Acquired data is transmitted via messages 388 and 390. Depending on the
870 signal strength and error detection, the gain of the amplifier 30 in the
wireless
transceiver can be adjusted via amplifier gain configuration message 392 and
when the change is made a gain configuration complete message 394 is sent back
to the base unit.
Wireless Electrode State Machine
875 Fig. 31 is a logic diagram = for a state machine running in the
microcontroller/DSP computing platform in the wireless electrode transceiver
assembly 20 of FIG. 2 and 3. When the device is powered up and running (and
acquiring bio-potential signals), the state machine is in an active mode 400.
The state
machine reacts to conditions that may be present, and responds to those
conditions as
880 shown in the figure. If the user plugs the transceiver assembly into the
programming
pin or interface on the base unit, the state machine goes into a reset mode
connection
state 402. This event prompts initiation of a set of routines that request
registration
with the base unit, as shown in 404. After registration procedures are
accomplished
(described elsewhere in this document), a sensor initialization routine 406 is
entered.
885 The routine 406 is shown in FIG. 33 and described subsequently. Then, a
sensor
activation routine 408 is entered, shown in FIG. 34. Finally a sensor data
acquisition
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ZILibsystem (DAQ) control routine 410 is entered, shown in FIG. 35.
Anottier event that triggers exit of the active mode state is when the base
uriit's "keep alive" or connection request signal is lost, as indicated at
412. This may
H90 occur for example when the patient moves out of range of the base unit
temporarily
or a problem occurs with the base unit. When this occurs, the microcontroller
enters the sensor DAQ control routine 410 and stops the acquisition of data.
(This
assumes that the memory size of the memory in the transceiver assembly 20 is
too
small to store significant amounts of data while contact with the base unit is
f11) 1-) interrupted; if sufficient memory capacity is present, the data could
continued to be
acquired and stored locally in the memory). The battery 45 is then switched to
a
power saving mode as indicated by routine 416.
Another event that can occur is the base unit's signal is regained as
indicated by condition 418. When this occurs, the state machine retums to
active
,)oo mode 400, as indicated by routine 420. The wireless transceiver assembly
enters a
base unit registration procedure 422, wherein the transceiver assembly re-
registers
with the base unit. If the base unit it is attempting to register with is not
its original
base unit (for example where the base unit's ID is different from the original
base
unit ID), then a routine 424 is entered in which the battery is switched to
power
savings mode. If the base unit is the original base unit, the sensor
activation and
dinta acquisition subsystem routines 408 and 410 of FIG. 33 and FIG. 34 are
entered.
While the electrode is in the active mode 400 state, it will normally be
receiving
the periodic connection request "keep alive" messages from the base unit. It
will issue
910 responses to those connection request messages periodically, as indicated
by a
connection request response routine 426.
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FIG. 32 is a logic diagrarn of a base unit state machine. The state machine
for
the base unit also includes an active mode 450. The base machine will respond
to
conditions including a sensor registration request condition 452. This
condition may
be entered during data acquisition or during initialization. The base unit
responds to
915 this condition by entering the sensor initialization, activation and
sensor DAQ control
routines 406, 408 and 410. After the registration is coinplete, the base unit
sends a
connection request message to all registered wireless transceiver assemblies
to insure
that they are still operational and within RF range of the base unit, as
indicated at 454.
If the signal from one of the wireless transceiver assemblies is lost, as
920 indicated by condition 453, then the sensor is deactivated from the system
as indicated
by 454. This step may be accompanied by an alarm or message on the user
interface
of the base unit.
If the signal is regained, as, indicated by condition 456, a sensor registered
routine 458 is entered to insure that the signal that is received originates
from a
925 registered transmitter assembly. Then, the =sensor activation and DAQ
control
routines 408 and 410 are entered.
Another condition that can occur is a noisy uplink or downlink channel,
represented by 460. When this occurs, the base unit enters a routine 462 in
which
available uplink or downlink channels are scanned and a low-noise channel is
930 selected. Then, a routine 464 is entered in which the new channel is
assigned to all
the registered and active wireless transceiver assemblies.
'Another event that can occur is a base unit configuration 466, which can
occur
in response to a prompt from a user. When this condition occurs, the state
machine
enters a routine 4678 that prompts the user to enter the configuration
information for
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935 the next wireless transceiver assembly. The sensor registration request
routine 452 is
transmitted to the wireless transceiver assembly on the control channel or via
the
programming interface. Sensor initialization and activation routines 406 and
410 are
tlien entered. If more transceiver assemblies are to be programmed; the
process
retums to step 468. If all of the assemblies have been programmed and
registered, as
940 indicated by routine 470, then.the system will enter a sensor DAQ control
routine 410
to start data acquisition and transmission, either automatically or in
response to input
from the user at the base unit user interface.
FIG. 33 is a illustration of the sensor initialization routine 406 of FIG. 31.
The
routine consists of a subroutine 500 that assigns a patient ID to the
transceiver
945 assembly. Next, a subroutine 502 is entered in which the functional
position of the
transceiver assembly is assigned by the base unit in response to user prompts.
A
sensor data acquisition rate assignment subroutine 504 is then entered. The
anti-
aliasing filter band is assigned by subroutine 506. Then the transceiver
assemblies are
synchronized by a global time base signal that is broadcast on the downlink
channel in
950 subroutine 508. Then, the base unit ID is assigned to the transceiver
assemblies by
subroutine 510 and the electrode ID values are registered with the base unit
in
subroutine 512. The order of execution of modules 500, 502, 504, 506, 508, 510
and
512 is not critical.
FIG. 34 illustrates the sensor activation routine 408 of FIG. 31 and 32. This
955 routine includes a subroutine.S14 that assigns the current data channel to
the wireless
transceiver assemblies. A subroutine 516 assigns a sensor-base unit
group/transmission ID for each of the wireless transceivers. Transceiver
amplification gain is assigned in subroutine 518. Then, a subroutine 520 is
entered
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that runs diagnostic tests on the wireless transceiver assemblies and
calibrates the
960 units accordingly.
The sensor data acquisition control routine 410 is shown in FIG. 35. This
routine consists of two parts, a start data acquisition subroutine and a stop
data
acquisition subroutine. The start data acquisition subroutine includes a first
module
522 that sends a command to the registered wireless transceiver assemblies to
start
965 data acquisition, and a second module 524 that commands the assemblies to
start data
transmission. The stop transmit of data subroutine includes a first module 526
that
commands the wireless transceiver to stop transmission of data, and a second
module
528 that commands the data acquisition subsystem to stop acquiring data.
Electrode system initialization/Onerations Management
970
The following is a pseudocode listing of system initialization and operations
management routines for the base unit and the electrodes, as an alternative
embodiment to the procedures of FIGs. 6 and 8.
975 Electrode power up / reactivation (battery attachment)
If no pre-stored channels is selected (first-time power up) or connection is
in
reset mode
Electrodes scan pre-set dedicated channel(s) for input signaling from
base unit.
980 Else
Start using pre-stored temporary transmit and receive channels for
messaging.
End
9e5 Base Unit power up - reactivation
If no pre-stored channels are selected, or reset mode connection is requested,
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or current traffic
Channel interference is high
Base Unit scans and selects a low-noise temporary transmit traffic
990 channel for all
electrodes to transmit signaling on.
Base Unit scans and selects a low-noise temporary receive traffic
channel for all
electrodes to receive signaling on.
995 Else
Use previously stored transmit and receive channels
End
Base Unit periodically transmits signaling on pre-set dedicated channel(s) if
electrode
1000 is not registered or disconnected, and listens (scans) for electrode
response. All other
transmission occurs on temporary trlafl<ic channels.
Send "keep-alive" signaling and scan for response from an electrode, then
For each electrode required for current configuration settings, once
detected (connection
1005 established)
Electrode is assigned a temporary identifier.
Electrode is associated with patient demographics info.
Electrode is assigned'a functional or anatomic position in the
monitoring
1010 system.
Electrode is requested to move to a new temporary transmit
traffic frequency
channel and time slot.
Electrode is requested to move to a new temporary receive
1015 traffic frequency
channel (and time slot if any).
End
End
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1020 If all required electrodes are registered and connected
Electrodes are assigned a (default/selected) data acquisition rate.
Electrodes are assigned a (default/selected) amplification gain setting.
Electrodes are assigned a (default/selected) filter band setting.
Run diagnostic system test to ensure quality of recordings
1025 Adjust amplification gain on electrodes until suitable signal strength is
obtained.
Adjust filter selection until good signal/noise ratio is obtained.
Run synchronization tests to ensure system is properly synchronized
for transfer
1030 of data test patterns.
End
Start data acquisition and monitoring.
End
1035
Base Unit may do any of the following during operation monitoring
Monitors and tracks for interference and bit error rate on current channel
setting, if too many
errors
1040 request retransmission of data in error due to interference, or if too
many errors then
select and move to new temporary transmit and/or receive channels,
Stops / restarts data acquisition for measured signals.
1045 Senses signal strength and re-adjust signal amplification gain
dynamically to
enable good
resolution on the A/D channels.
Interrupts data acquisition for reconfiguration or re-initialization
procedures.
Switches electrode(s) into power saving mode or reactivates electrode(s)
1050 operation.
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Persons skilled in the art will appreciate that the details of the presently
preferred embodiment described herein can be changed and modified without
departure from the spirit and scope of the invention. The system 10 is readily
adapted
1055 to acquiring other types of physiologic, chemical, physical or electrical
processes,
such as temperature, blood pressure, glucose, respiratory parameters, etc. The
wireless sensors could be either placed on the patient's body or implanted. In
this
case, the wireless transceiver may connect to a different type of physiologic
sensor
which converts a measured parameter to a voltage (or this functionality could
be
1060 incorporated in the wireless transceiver assembly) and transmits the
signal to a base
unit. This true spirit and scope is to be determined by reference to the
appended
claims.
1065
1070
44
