MEDICAL DEVICE FOR DETERMINING THE POSTURE OF PATIENT

• US 20100113961A1
• Filed: 06/29/2005
• Published: 05/06/2010
• Est. Priority Date: 06/29/2005
• Status: Active Grant

• Current Assignee: St. Jude Medical AB (Abbott Laboratories Incorporated)
• Original Assignee: St. Jude Medical AB (Abbott Laboratories Incorporated)
• Inventors: Norén, Kjell, Öhlander, Malin, Holmström, Nils
• Granted Patent: US 8,790,254 B2
• Time in Patent Office: Days
• US Class Current: 600/547
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/1116 Determining posture transitions
• CPC Class Codes: A61B 5/4561 Evaluating static posture, e.g. undesirable back curvature A61B5/1116 takes precedence
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: G16H 20/30 relating to physical therapies or activities, e.g. physiotherapy, acupressure or exercising

Abstract

The present invention relates to a method for determining the posture of a patient. The method comprises the steps of: initiating (50, 52) a patient posture determining session by performing an electrical bio-impedance measurement session in at least one of a number of different electrode configurations in order to measure an impedance value for the at least one configuration; obtaining reference impedance values (54) stored in advance for the at least one configuration and for at least one potential posture of the patient; comparing (54) the measured impedance value for the at least one configuration with corresponding stored reference impedance values for at least one potential posture of the patient; and determining (56) the present posture of the patient by using results from the comparison between measured impedance values and the stored reference impedance values. Furthermore, the invention relates to a medical device for determining the posture of a patient and a computer readable medium comprising instructions for bringing a computer to perform the inventive method.

Claims

1. A method for determining the posture of a patient characterized by the steps of

initiating (50, 52) a patient posture determining session by performing an electrical bio-impedance measurement session in at least one of a number of different electrode configurations in order to measure an impedance value for said at least one configuration;

obtaining (54) reference impedance values stored in advance for said at least one configuration and for at least one potential posture of said patient;

comparing (54) said measured impedance value for said at least one configuration with corresponding stored reference impedance values for at least one potential posture of said patient; and

determining (56) the present posture of the patient by using results from said comparison between measured impedance values and said stored reference impedance values.

2. The method according to claim 1, further comprising the steps of

obtaining reference impedance values, wherein at least one reference impedance value is obtained for each of a predetermined number of electrode configurations and each of a predetermined number of postures;

and

storing said reference impedance values in a reference value matrix, said matrix containing reference impedance values for each electrode configuration and each potential posture.

3. The method according to claim 1, further comprising the steps of:

checking whether a difference between said measured impedance value for said at least one configuration and said corresponding stored reference impedance values is within a predetermined interval; and

if said difference is outside said interval at a predetermined number of posture determining sessions, updating said stored reference impedance values by using said measured impedance values of said predetermined number of posture determining sessions.

4. The method according to claim 2, wherein the step of measuring reference impedance values comprises the steps of:

sensing the breathing rate of the patient; and

performing an impedance measurement session for each reference impedance value, wherein each value is calculated as a mean value of the measured impedance signal over a predetermined number of breaths.

5. The method according to claim 2, wherein the step of measuring reference impedance values comprises the steps of:

sensing the breathing rate of the patient; and

performing an impedance measurement session for each reference impedance value, said measurement being synchronized with the breathing of said patient, wherein each value is calculated as a mean value of the measured impedance signal over a predetermined number of breathing cycles.

6. The method according to claim 2, wherein the step of measuring reference impedance values comprises the step of:

performing an impedance measurement session for each reference impedance value, wherein each value is calculated as a mean value of the measured impedance signal over a predetermined period of time.

7. The method according to any one of claims 1-6, wherein the step of initiating comprises the steps of:

sensing the breathing rate of the patient, and

calculating said impedance value for said at least one configuration as a mean value of the measured impedance signal over a predetermined number of breaths.

8. The method according to any one of claims 1-6, wherein the step of initiating comprises the steps of

sensing the breathing rate of the patient,

synchronizing said impedance measurement session with the breathing of said patient;

and

calculating said impedance value for said at least one configuration as a mean value of the measured impedance signal over a predetermined number of breathing cycles.

9. The method according to any one of claims 1-6, wherein the step of initiating comprises the steps of:

calculating said impedance value for said at least one configuration as a mean value of the measured impedance signal over a predetermined period of time.

10. The method according to any one of preceding claims, wherein the step of comparing comprises the step of

calculating a deviation factor for said at least one potential posture using said corresponding measured impedance values and stored reference impedance values, wherein said deviation factor for said at least one potential posture is used to determine the present posture.

11. The method according to claim 4, wherein the step of calculating a deviation factor comprises the step of:

calculating a square difference sum for said at least one potential posture using said measured impedance values and stored reference impedance values, wherein said deviation factor corresponds to said square difference sum.

12. The method according to claim 5, wherein the step of determining the present posture comprises the steps of:

identifying the potential posture of said at least one potential postures having the lowest square difference sum; and

determining the present posture of the patient as the potential posture having the lowest square difference.

13. The method according to claim 5, wherein the step of determining the present posture comprises the steps of

checking whether said square difference for said at least one potential posture is within a predetermined interval;

and

determining the present posture of the patient to the potential posture having a square difference sum within said predetermined interval.

14. The method according to any one of preceding claims, further comprising the steps of:

sensing a heart rate of said patient;

determining whether said heart rate is within a predetermined heart rate interval; and

initiating said patient posture determining session if said sensed heart rate is within said predetermined heart rate interval.

15. The method according to any one of preceding claims, further comprising the steps of

sensing an activity level of said patient;

determining whether said activity level is below a predetermined activity level; and

initiating said patient posture determining session if said sensed activity level is below said predetermined activity level.

16. The method according to any one of preceding claims, further comprising the steps of

sensing a body temperature of said patient;

and

determining whether said temperature is within a predetermined temperature level interval; and

initiating said patient posture determining session if said sensed body temperature is within said predetermined temperature level interval.

17. The method according to any one of preceding claims, further comprising the steps of:

sensing signals related to heart pumping activity of said patient;

determining cardiac output based on said signals;

determining whether said cardiac output is within a predetermined cardiac output level interval; and

initiating said patient posture determining session if said sensed cardiac output is within said predetermined cardiac output level interval.

18. The method according to any one of preceding claims, further comprising the step of:

sending an updating indication signal indicating that said reference impedance values require an updating if a posture not have been determined in a patient posture determining session during a predetermined period of time.

38. A computer program product, which when executed on a computer, performs steps in accordance with any one of claim 1-18

39. Computer readable medium comprising instructions for bringing a computer to perform a method according to any one of the preceding claims 1-18.

19. A medical device for determining the posture of a patient, said device being connectable to a patient in a number of different electrode configurations, characterized by means for measuring an electrical bio-impedance (29) at each of said number of electrode configurations, wherein said means for measuring an impedance (29) is adapted to, upon receiving a triggering signal, initiate a patient posture determining session by performing an impedance measurement session in at least one of said electrode configurations in order to measure an impedance value for said at least one configuration;

and

processing means (30) including;

means for obtaining (30) reference impedance values stored in advance in a storing means (31) for said at least one configuration and for at least one potential posture of said patient;

means for comparing (35) said measured impedance values with corresponding stored reference impedance values for at least one potential posture of said patient; and

means for determining (37) the present posture of the patient by using results from said comparison between measured impedance values and said stored reference impedance values.

20. The device according to claim 19, wherein said processing means is adapted to bring said impedance measuring means to measure at least one reference impedance value for each of a predetermined number of electrode configurations and each of a predetermined number of postures, said measured reference impedance values being stored in a reference value matrix in said storing means, wherein said matrix contains reference impedance values for each electrode configuration and each potential posture

21. The device according to claim 19, wherein said processing means further comprises means for checking whether a difference between said measured impedance value for said at least one configuration and said corresponding stored reference impedance values is within a predetermined interval;

and wherein said processing means is adapted to, if said difference is found to be outside said interval at a predetermined number of posture determining sessions, update said stored reference impedance values by using said measured impedance values of said predetermined number of posture determining sessions.

22. The device according to any one of preceding claim 19-21, further comprising:

means for sensing the breathing rate of the patient (39).

23. The device according to claim 22, wherein processing means is adapted to bring said impedance measurement means to perform an impedance measurement session for each reference impedance value, wherein each value is calculated as a mean value of the measured impedance signal over a predetermined number of breaths.

24. The device according to claim 22, wherein said processing means is adapted to bring said impedance measurement means to perform an impedance measurement session for each reference impedance value synchronized with the breathing of said patient, wherein each value is calculated as a mean value of the measured impedance signal over a predetermined number of breathing cycles.

25. The device according to claim 19, wherein said processing means is adapted to bring said impedance measurement means to perform an impedance measurement session for each reference impedance value, wherein each value is calculated as a mean value of the measured impedance signal over a predetermined period of time.

26. The device according to any one of claims 22-25, wherein said processing means is adapted to bring said impedance measurement means to perform an impedance measurement session for each impedance value, said impedance value for said at least one configuration being calculated as a mean value of the measured impedance signal over a predetermined number of breaths.

27. The device according to any one of claims 22-25, wherein said processing means is adapted to bring said impedance measurement means to synchronize said impedance measurement sessions with the breathing of said patient, said impedance value for said at least one configuration being calculated as a mean value of the measured impedance signal over a predetermined number of breathing cycles.

28. The device according to any one of claims 19-25, wherein said processing means is adapted to bring said impedance measurement means to perform an impedance measurement session for each impedance value, said impedance value for said at least one configuration being calculated as a mean value of the measured impedance signal over a predetermined period of time.

29. The device according to any one of preceding claims 19-28, wherein said processing means further comprises means for calculating a deviation factor for said at least one potential posture using said corresponding measured impedance values and stored reference impedance values, wherein said deviation factor for said at least one potential posture is used to determine the present posture.

30. The device according to claim 29, wherein said calculating means is adapted to calculate a square difference sum for said at least one potential posture using said measured impedance values and stored reference impedance values, wherein said deviation factor corresponds to said square difference sum.

31. The device according to claim 30, wherein said determining means is adapted to

identify the potential posture of said at least one potential postures having the lowest square difference sum;

and

determine the present posture of patient as the potential posture having the lowest square difference.

32. The device according to claim 30, wherein said determining means is adapted to check whether said square difference for said at least one potential posture is within a predetermined interval;

and

determine the present posture of patient to the potential posture having a square difference sum within said predetermined interval.

33. The device according to any one of preceding claims 19-32, further comprising

means for sensing a heart rate of said patient (41);

and wherein said processing means is adapted to determine whether said heart rate is within a predetermined heart rate interval; and

bring said impedance measurement means to initiate said patient posture determining session if said sensed heart rate is within said predetermined heart rate interval.

34. The method according to any one of preceding claims 19-33, further comprising

means for sensing an activity level of said patient;

and wherein said processing means is adapted to determine whether said activity level is below a predetermined activity level;

and bring said impedance measurement means to initiate said patient posture determining session if said sensed activity level is below said predetermined activity level.

35. The device according to any one of preceding claims 19-34, further comprising

means for sensing a body temperature of said patient;

and wherein said processing means is adapted to determine whether said temperature is within a predetermined temperature level interval; and

bring said impedance measurement means to initiate said patient posture determining session if said sensed body temperature is within said predetermined temperature level interval.

36. The device according to any one of preceding claims 19-35, further comprising:

means for sensing signals related to heart pumping activity of said patient; and

wherein said processing means is adapted to determine the cardiac output based on said signals;

determine whether said cardiac output is within a predetermined cardiac output level interval; and

bring said impedance measurement means to initiate said patient posture determining session if said sensed cardiac output is within said predetermined cardiac output level interval.

37. The method according to any one of preceding claims 19-36, further comprising alarm means being adapted to send an updating indication signal indicating that said reference impedance values require an updating if a posture not have been determined in a patient posture determining session during a predetermined period of time.