Architecture for TDMA medical telemetry system

• US 5,944,659 A
• Filed: 07/02/1996
• Issued: 08/31/1999
• Est. Priority Date: 11/13/1995
• Status: Expired due to Term

• Current Assignee: GE Medical Systems Information Technologies Incorporated (General Electric Company)
• Original Assignee: VitalCom, Inc. (General Electric Company)
• Inventors: Flach, Terry E., Stoop, Michael D.
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US08/675,594
• Time in Patent Office: 1,155 Days
• Field of Search: 128/630, 128/903, 128/904, 128/637, 128/638, 128/670, 128/671, 128/731-733, 128/739-741
• US Class Current: 600/300
• CPC Class Codes: A61B 2560/0209 adapted for power saving
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/002 Monitoring the patient using a local or closed circuit, e.g. in a room or building A61B5/0017 takes precedence
• CPC Class Codes: A61B 5/1113 Local tracking of patients, e.g. in a hospital or private home
• CPC Class Codes: H03L 3/00 Starting of generators
• CPC Class Codes: H03L 7/10 for assuring initial synchronisation or for broadening the capture range
• CPC Class Codes: H03L 7/14 for assuring constant frequency when supply or correction voltages fail or are interrupted
• CPC Class Codes: H04B 1/1615 Switching on; Switching off, e.g. remotely battery saving circuits associated with selective call operation H04W52/00; details of power consumption reduction in a PLL, H03L7/0802, H03L7/14, H03L2207/08, H03L2207/18; muting amplifiers by gain control see H03G3/34
• CPC Class Codes: H04W 52/028 switching on or off only a part of the equipment circuit blocks
• CPC Class Codes: Y02D 30/70 in wireless communication networks
• CPC Class Codes: Y10S 128/903 Radio telemetry
• CPC Class Codes: Y10S 128/904 Telephone telemetry

Abstract

A medical telemetry system is provided for collecting the real-time physiologic data of patients (including ambulatory patients) of a medical facility, and for transferring the data via RF to a real-time data distribution network for monitoring and display. The system includes battery-powered remote telemeters which attach to respective patients, and which collect and transmit (in data packets) the physiologic data of the patients. The remote telemeters communicate bi-directionally with a number of ceiling-mounted RF transceivers, referred to as "VCELLs," using a wireless TDMA protocol. The VCELLs, which are hardwire-connected to a LAN, forward the data packets received from the telemeters to patient monitoring stations on the LAN. The VCELLs are distributed throughout the medical facility such that different VCELLs provide coverage for different patient areas. As part of the wireless TDMA protocol, the remote telemeters continuously assess the quality of the RF links offered by different nearby VCELLs (by scanning the frequencies on which different VCELLs operate), and connect to those VCELLs which offer the best link conditions. To provide a high degree of protection against multi-path interference, each remote telemeter maintains connections with two different VCELLs at-a-time, and transmits all data packets (on different frequencies and during different timeslots) to both VCELLs; the system thereby provides space, time and frequency diversity on wireless data packet transfers from the telemeters. The telemeters and VCELLs also implement a patient location protocol for enabling the monitoring of the locations of individual patients. The architecture can accommodate a large number of patients (e.g., 500 or more) while operating within the transmission power limits of the VHF medical telemetry band.

Claims

1. A medical telemetry system for permitting real-time monitoring of patients, including ambulatory patients, of a medical facility from a centralized monitoring station, comprising:

at least one monitoring station which displays real-time physiologic data of multiple patients;

a plurality of battery-powered wireless remote telemeters, the remote telemeters configured to attach to, and configured to collect and transmit real-time physiologic data of, respective patients; and

a plurality of transceivers which communicate bi-directionally with the plurality of remote telemeters using a plurality of wireless radio frequency (RF) channels, the transceivers connected to the at least one monitoring station and being distributed throughout the medical facility such that different transceivers provide data-reception coverage for different areas of the medical facility, at least some of the transceivers receiving physiologic data on different RF channels, the transceivers configured to receive the physiologic data transmitted by the remote telemeters and to forward the physiologic data over a wired connection to the at least one monitoring station;

wherein at least some of the remote telemeters automatically switch between different RF channels of the plurality of RF channels in response to patient movement throughout the medical facility to connect to and disconnect from individual transceivers of the plurality of transceivers.

2. The medical telemetry system according to claim 1, wherein at least some of the remote telemeters evaluate wireless link conditions offered by different transceivers and establish wireless connections with individual transceivers based at least upon said wireless link conditions.

3. The medical telemetry system according to claim 2, wherein at least one remote telemeter of the plurality of remote telemeters maintains wireless connections with at least two different transceivers at-a-time, and transmits the physiologic data of a respective patient to the at least two different transceivers to provide at least spacial diversity.

4. The medical telemetry system according to claim 2, wherein the remote telemeters communicate with the transceivers using a TDMA protocol, and the at least one remote telemeter transmits the physiologic data to the at least two different transceivers during different respective TDMA timeslots to thereby additionally provide time diversity.

5. The medical telemetry system according to claim 4, wherein the at least one remote telemeter transmits the physiologic data to the at least two different transceivers on different RF frequencies, the different RF frequencies spaced sufficiently apart to provide frequency diversity.

6. The medical telemetry system according to claim 1, wherein the transceivers forward the physiologic data to the at least one monitoring station over a local area network.

7. The medical telemetry system according to claim 1, wherein at least two of the transceivers communicate with the remote telemeters on the same RF channel.

8. The medical telemetry system according to claim 7, wherein the at least two transceivers which communicate on the same RF channel are sufficiently spaced apart to avoid interference with one another.

9. The medical telemetry system according to claim 1, wherein at least some of the transceivers of the plurality of transceivers are synchronized with one another.

10. The medical telemetry system according to claim 1, wherein different subsets of the plurality of transceivers are connected to respective concentrator computers, each concentrator computer receiving physiologic data from a respective subset of transceivers and forwarding the physiologic data to the at least one monitoring station.

11. The medical telemetry system according to claim 10, wherein the concentrator computers are interconnected by a local area network.

12. The medical telemetry system according to claim 11, wherein the local area network comprises a plurality of monitoring stations which display the real-time physiologic data of the patients.

13. The medical telemetry system according to claim 1, wherein the remote telemeters communicate with the transceivers using a TDMA protocol, and at least one of the transceivers broadcasts timeslot availability messages to the remote telemeters, the timeslot availability messages indicating available and unavailable TDMA timeslots for communicating with the at least one transceiver.

14. The medical telemetry system according to claim 13, wherein different transceivers of the plurality broadcast timeslot availability messages to the remote telemeters on different RF frequencies.

15. The medical telemetry system according to claim 1, wherein the plurality of transceivers communicate with the plurality of remote telemeters within a VHF medical telemetry band.

16. The medical telemetry system according to claim 1, wherein at least one of the remote transceivers maintains wireless connections with multiple remote telemeters at-a-time.

17. The medical telemetry system according to claim 1, wherein at least one of the remote transceivers is positioned proximate to a known intermittent source of electromagnetic interference.

18. The medical telemetry system according to claim 17, wherein the at least one remote transceiver is positioned within a patient X-ray room.

19. The medical telemetry system according to claim 1, wherein at least some of the transceivers transmit patient location signals to the remote telemeters.

20. The medical telemetry system according to claim 1, wherein at least one remote telemeter of the plurality of remote telemeters includes a processor which executes a control program to implement a wireless communications protocol in which the remote telemeter transmits data packets to different transceivers during different timeslots, the control program configured to maintain wireless connections with at least two different transceivers at-a-time on at least two different RF channels, and to transmit data packets that contain like physiologic data to the at least two different transceivers to provide multiple simultaneous transmission paths for the transfer of the physiologic data between the remote telemeter and the monitoring station.

21. A method of transferring real-time physiologic data of a patient from a wireless remote telemeter to a receiving node of a network so as to provide protection against multi-path interference, the remote telemeter configured to attach to the patient, the method comprising:

providing first and second transceivers that are positioned within respective first and second patient areas of a medical facility, the patient areas being sufficiently close to one another so that the transceivers provide overlapping first and second coverage zones, each transceiver positioned remotely from and being connected to the receiving node;

transmitting a first data packet from the remote telemeter to the first transceiver during a first timeslot, the first data packet containing at least the real-time physiologic data;

transmitting a second data packet from the remote telemeter to the second transceiver during a second timeslot which is different from the first timeslot, the second data packet containing at least the real-time physiologic data;

forwarding the first and second data packets, respectively, from the first and second transceivers to the receiving node; and

selecting between the first and second data packets at the receiving node.

22. The method according to claim 21, wherein the first and second data packets contain respective error detection codes, and the step of selecting comprises evaluating the error detection codes at the receiving node to determine whether the first and second data packets were successfully received by the first and second transceivers.

23. The method according to claim 22, wherein the error detection codes comprise error correction codes.

24. The method according to claim 21, wherein the step of transmitting the first data packet is performed on a first frequency channel and the step of transmitting the second data packet is performed on a second frequency channel, the first and second frequency channels sufficiently different to provide frequency diversity.

25. The method according to claim 24, wherein the first and second frequency channels fall within a VHF medical telemetry band.

26. The method according to claim 21, further comprising sending either the first data packet or the second data packet from the receiving node to a patient monitoring station over a wired local area network.

27. The method according to claim 21, wherein the step of forwarding the first and second data packets to the receiving node comprises transmitting the packets over different respective wired connections.

28. The method according to claim 21, wherein the steps of transmitting first and second packets from the remote telemeter are repeated periodically to transmit the patient'"'"'s ECG waveform data in real-time to the receiving node.

29. The method according to claim 21, further comprising:

positioning a third transceiver within a third patient area to provide a third coverage zone which overlaps with the first and second coverage zones, the third transceiver positioned remotely from and being connected to the receiving node; and

in response to patient movement away from the first patient area towards the third patient area, automatically establishing a connection between the remote telemeter and the third transceiver and terminating a connection between the remote telemeter and the first transceiver.

30. The method according to claim 29, wherein the step of establishing a connection with the third transceiver comprises sending a timeslot request message from the remote telemeter to the third transceiver.

31. The method according to claim 29, wherein the step of establishing a connection with the third transceiver comprises:

broadcasting a timeslot availability message from the third transceiver, the timeslot availability message indicating available and unavailable timeslots for communicating with the third transceiver; and

receiving the timeslot availability message with the remote telemeter, and evaluating the timeslot availability message to identify an available timeslot.

32. The method according to claim 29, wherein the first, second and third transceivers communicate with the remote telemeter on different respective frequency channels.

36. The medical telemetry system according to claim 32, wherein each transceiver is configured to concurrently receive the physiologic data of multiple patients from multiple telemeters.

33. A medical telemetry system for monitoring patients of a medical facility, the system comprising:

a plurality of transceivers distributed throughout the medical facility such that different transceivers provide data reception coverage for different areas of the medical facility, the plurality of transceivers connected to a common data receiving node, at least some of the transceivers of the plurality operating on different radio frequency (RF) channels; and

a wireless remote telemeter that is configured to be worn by an ambulatory patient, the remote telemeter including sensing circuitry for sensing physiologic data of the patient, the remote telemeter implementing a wireless communications protocol in which the remote telemeter transmits data packets to different transceivers of the plurality during different timeslots, and in which the remote telemeter maintains wireless connections with at least two different transceivers at-a-time on at least two different RF channels and transmits like physiologic data to the at least two different transceivers to provide multiple concurrent transmission paths for the transfer of the physiologic data from the remote telemeter to the receiving node.

34. The medical telemetry system according to claim 33, wherein the remote telemeter implements a switch-over protocol in which the remote telemeter automatically connects to and disconnects from different transceivers of the plurality based on assessments of RF link conditions.

35. The medical telemetry system according to claim 33, wherein the physiologic data comprises ECG waveform data, and the remote telemeter transmits the ECG waveform data to the at least two different transceivers in real-time.