Method of identifying valid signal-carrying channels in a cardiorespiratory alert system

• US 5,564,429 A
• Filed: 09/20/1994
• Issued: 10/15/1996
• Est. Priority Date: 11/25/1991
• Status: Expired due to Fees

• Current Assignee: Vitalscan Incorporated
• Original Assignee: Vitalscan Incorporated
• Inventors: Worth, Laura A., Bornn, Robert, Levinsky, Jeff L., Ricks, Robert D.
• Primary Examiner(s): Zele, Krista M.
• Assistant Examiner(s): Casler, Brian L.
• Application Number:
  US08/309,253
• Time in Patent Office: 756 Days
• Field of Search: 128/696, 128/639, 128/644, 128/670, 128/700, 128/642, 128/901, 607/152, 607/142, 607/15, 607/16, 607/28
• US Class Current: 600/508
• CPC Class Codes: A61B 2560/0209 adapted for power saving
• CPC Class Codes: A61B 2562/222 Electrical cables or leads therefor, e.g. coaxial cables or ribbon cables
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/1135 by monitoring thoracic expansion
• CPC Class Codes: A61B 5/282 Holders for multiple electrodes for introduction into the body A61B5/287
• CPC Class Codes: A61B 5/411 Detecting or monitoring allergy or intolerance reactions to an allergenic agent or substance
• CPC Class Codes: A61B 5/6831 Straps, bands or harnesses
• CPC Class Codes: A61B 5/747 in case of emergency, i.e. alerting emergency services
• CPC Class Codes: G16H 40/63 for local operation
• CPC Class Codes: G16H 40/67 for remote operation
• CPC Class Codes: G16Z 99/00 Subject matter not provided for in other main groups of this subclass
• CPC Class Codes: Y10S 128/903 Radio telemetry
• CPC Class Codes: Y10S 128/904 Telephone telemetry

Abstract

A cardiorespiratory alert system is described which comprises a patient unit which communicates with a caregiver unit, via an optional central base station in a Hospital Configuration, or via a base station in an Alternate Site/Home Configuration. A number of techniques are employed to provide a system which provides alerts to the caregiver unit when life-threatening conditions are detected in the patient, yet is tolerant to the presence of artifact so that false positives are reduced. The present invention utilizes patient cooperation as well as a number of artifact reducing mechanisms to provide increased immunity to artifact.

Claims

1. A method for identifying which channels from among a plurality of ecg signal-carrying channels are carrying valid information, wherein each channel has a ecg signal comprising a series of beats which are separated from one another, the method comprising the steps of

maintaining a set of valid channels each of which has beats which are separated from one another by no more than a predetermined amount;

searching among the plurality of ecg signal-carrying channels for channels with regular beats whenever there is only one or no valid channels in the set of valid channels;

periodically checking the channels in the valid set to determine whether the separation between beats in the valid channels exceeds a maximum pulse separation amount;

removing channels from the valid set which have beat separations which exceed the maximum pulse separation amount;

adding a channel from among the plurality of ecg signal-carrying channels to the valid set when a new beat for that channel is within a synch_-- factor of a latest beat for the channels already in the valid set of channels;

rejecting a channel from among the plurality of ecg signal-carrying channels from inclusion in the valid set when a new beat for that channel is not within a synch_-- factor of the latest beat for the channels already in the valid set of channels; and

issuing as an output a selected beat from a valid channel, where the selected beat is the most recently received of the beats of the valid channels.

2. The method of claim 1 wherein the step of searching for valid channels includes the steps of

determining an average interval between beats in the channel;

determining whether an interval between any two sequential beats exceeds a predetermined maximum variability amount; and

designating as valid those channels in which none of the intervals between any two sequential beats exceed the predetermined maximum variability amount.

3. The method of claim 2 further including the steps of

checking the channels within the valid set for regular beats;

and

removing the channels from the valid channel set when regular beats are not found in any of the channels in the valid set;

searching any channel not in the valid set for regular beats, including the steps of

outputting the beats from any channel for which regular beats are found; and

placing the channel for which regular beats are found into the valid channel set.

4. The method of claim 1 wherein the signals being evaluated further include pulse signals.

5. A method for identifying which channels from among a plurality of pulse signal-carrying channels are carrying valid information, wherein each channel has a pulse signal comprising a series of beats which are separated from one another, the method comprising the steps of,

maintaining a set of valid channels each of which has beats which are separated from one another by no more than a predetermined amount;

searching among the plurality of pulse signal-carrying channels for channels with regular beats whenever there is only one or no valid channels in the set of valid channels;

periodically checking the channels in the valid set to determine whether the separation between beats in the valid channels exceeds a maximum pulse separation amount;

removing channels from the valid set which have beat separations which exceed the maximum pulse separation amount;

adding a channel from among the plurality of pulse signal-carrying channels to the valid set when a new beat for that channel is within a synch_-- factor of a latest beat for the channels already in the valid set of channels;

rejecting a channel from among the plurality of pulse signal-carrying channels from inclusion in the valid set when a new beat for that channel is not within a synch_-- factor of the latest beat for the channels already in the valid set of channels; and

issuing as an output a selected beat from a valid channel, where the selected beat is the most recently received of the beats of the valid channels.