Implantable medical device for tracking patient functional status

• US 6,045,513 A
• Filed: 05/13/1998
• Issued: 04/04/2000
• Est. Priority Date: 05/13/1998
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Padmanabhan, Vasant, Stone, Karen A.
• Primary Examiner(s): KAMM, WILLIAM E
• Application Number:
  US09/078,221
• Time in Patent Office: 692 Days
• Field of Search: 600/508
• US Class Current: 600/508
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/1118 Determining activity level
• CPC Class Codes: A61B 5/7232 involving compression of the physiological signal, e.g. to extend the signal recording period
• CPC Class Codes: G16H 40/63 for local operation
• CPC Class Codes: G16H 40/67 for remote operation
• CPC Class Codes: G16H 50/30 for calculating health indices; for individual health risk assessment

Abstract

An implantable medical device determines activity levels over a set of time periods, preferably on the order of seconds, minutes and hours and a display is enabled for days or weeks at recorded activity levels over a range of dates. This enables physician review of patient functional status. Additional physiologic data can be recorded along with the activity data, and this too may be reported out from the implanted device to a medical communications system for alarm purposes, titrating drugs or other monitoring tasks.

Claims

1. An implantable medical device useful for tracking patient functional status by displaying values upon which an evaluation of said functional status can be made, said implantable medical device comprising a housing having an activity sensor and circuitry therein for recording output from said activity sensor wherein said output is compressed in accord with a processing circuit constructed to operate a procedure to iteratively, after the expiry of each of a first size time interval:

add up via a summation means a number of activity counts sensed per a first one of each first time size intervals to produce a first sum, and if said first sum is greater than a predetermined value, storing a count value representing the result of comparing said first time size interval first sum to said predetermined value in a memory means,

then to repeat this add up procedure for subsequent ones of said first time size intervals and to store a first time size interval count value for said first size time intervals occurring within a second size time interval in said memory means,

then to determine via a computation means a first display value for a representation of said stored first time size interval count values, and storing said first display value representing a total value for said second time size interval.

2. A device as set forth in claim 1 further comprising means for providing said first display values to a display means for displaying a second display value wherein said second display value is a sum of said first display values.

3. A device as set forth in claim 1 wherein said implantable medical device has an alarm circuit which can function to become active based on checking an alarm flag value in a memory and wherein said processing circuit is adapted to operate said procedure to further iteratively determine if said first display value is a predetermined function of a predetermined alarm value, and for storing a result of said determination, and for setting said alarm flag value based on the result of said determination.

4. A device as set forth in claim 3 wherein further comprising a patient-alarm alarm interface which is activated when said alarm flag value equals a predetermined alarm flag activation value.

5. A device as set forth in claim 4 wherein said patient-alarm interface is an audible sound generator.

7. A device as set forth in claim 1 wherein said processing circuit is adapted to further determine if activity values represented by said first display values match a programmable pattern of activity level, and to set a flag indicating such a change.

8. A device as set forth in claim 1 wherein said housing further comprises additional sensor means for measuring values of additional physiologic parameters and producing measurement output therefrom, and wherein said processing circuit constructed to operate said procedure processes and stores in said memory, temporally related to said first display values, additional physiologic measurement values taken from said additional sensor means output.

9. A device as set forth in claim 8 wherein said additional sensors are appropriately adapted and disposed connection with and in relation to said housing and said circuitry to sense and to record in said memory, physiologic signals including any of those drawn from the set of possible sensor signals including arrhythmias, arrhythmias during rest periods, respiration rate during rest periods, respiration rate, occurrence of abnormal breathing episodes during rest, change in sinus rate during rest, heart rate variability, blood pressure, ST segment variation, blood oxygenation, and temperature.

10. A device as set forth in claim 1 wherein said housing further comprises additional sensor means for measuring values of additional physiologic parameters of a patient into which said device may be implanted and producing measurement output therefrom, and wherein said circuitry for processing and storing values processes and stores temporally related to said first display values, additional physiologic measurement values taken from said additional sensor means output.

11. A medical system, as set forth in any one of claims 1-7, 8, 9, or 10 further comprising a receiving device for receiving patient data from said implant including representations of said first display values having a communications link to a communications system to enable the communication of said representation of said first display values to a remote device for subsequent display.

6. A device as set forth in clam 5 wherein said audible sound generator comprises speech generator means adapted to produce intelligible speech.

12. An implantable medical device (IMD) comprising means for tracking activity counts generated by an activity sensor in said IMD over small units of time and means for storing a compilation of values related to combined sums of said activity counts for a sum of said small units of time over larger units of time and having means for detecting and for recording arrhythmic cardiac events such that said compilation of values is stored with an indication of temporal relatedness to any arrhythmic events which may be detected and recorded by said means for detecting and recording substantially contemporaneously with the storing of said compilation of values.

13. An implantable medical device having an activity crystal for determining a counts value for each "a" second period based on activity sensed by said activity crystal, a processing circuit for averaging each said counts value over the number of a second counts in each minute, and for generating an average counts value therefrom, and a memory circuit for storing a positive activity value for said average counts value for each minute if said average counts value is greater than a predetermined value.

14. An implantable medical device as set forth in claim 13 further comprising a processing circuit for storing a sum of all said positive activity values.

22. A method as set forth in claim 13 further comprising communication the first display values to an external device.

23. A method as set forth in claim 22 further comprising activating an alarm system in said external device wherein said alarm system sets a flag indicating a need to take corrective action if the display values received by said external device alarm system match a predetermined pattern.

15. A device adapted for affixation to a patient for tracking patient functional status by producing display values upon which an evaluation of said functional status can be made, said device comprising a housing having an activity sensor and circuitry therein for recording output from said activity sensor wherein said output is compressed in accord with a processing circuit constructed to operate a procedure to iteratively, after the expiry of each of a first size time interval:

add up via a summation means a number of activity counts sensed per a first one of each first size time intervals to produce a first sum, and if said first sum is greater than a predetermined value, storing a count value representing the result of comparing said first size time interval first sum to said predetermined value in a memory means,

then to repeat this add up procedure for subsequent ones of said first size time intervals and to store a count value for said first size time intervals occurring within a second size time interval,

then to determine via a computation means a first display value for a representation of said stored count values, and storing said first display value representing a total value for said second size time interval.

16. A method of tracking patient functional status by enabling a display upon which an evaluation of functional status can be made comprising:

measuring activity counts with an implantable activity sensor,

recording output from said activity sensor said output is compressed in accord with a procedure which iteratively, after the expiry of each of a first size time interval;

adds up a number of activity counts sensed per a first one of each first time intervals to produce a first sum, and if said first sum is greater than a predetermined value, storing a count value representing the result of comparing said first time interval first sum to said predetermined value in a memory means,

then repeating this add up procedure for subsequent ones of said first size intervals and storing a count value for said first size time intervals occurring within a second size time interval,

then determining a first display value for a representation of said count values from said ad up procedure, and

storing said first display value.

17. A method as set forth in claim 16 further comprising providing said first display values to a display means, then generating a second display value comprising a representation of a sum of said first display values for a diurnal time period, and then displaying said second display value.

18. A method as set forth in claim 16 comprising the additional steps of:

(a) further iteratively determining if said first display value is a predetermined function of a predetermined alarm value,

(b) storing a result of said determination, and,

(c) then setting an alarm flag representing the result of said determination.

19. A method as set forth in claim 18 wherein if said alarm value flag is set, activating a patient alarm to notify the patient.

20. A method for displaying representations of said first display values generated by any of the methods as set forth in any one of claims 16 or 17-19, further comprising the step of receiving said first display values for generating a display, and adding up all the first display values for a diurnal period and displaying a visual representation of said value of said sum for each said diurnal period in a range of diurnal periods.

21. The method for displaying representations of said first display values generated by any of the methods as set forth in any one of claims 16 or 17, 19 further comprising the intermediate step of averaging all said diurnal period values for a week and then displaying a visual representation of the value of the week average for the week.