Respiration measurement by means of morphological operators

• US 8,419,645 B2
• Filed: 07/05/2011
• Issued: 04/16/2013
• Est. Priority Date: 10/16/2008
• Status: Expired due to Fees

• Current Assignee: Biotronik SE & Company KG
• Original Assignee: Biotronik VI Patent AG (Biotronik SE & Company KG)
• Inventors: Lian, Jie, Muessig, Dirk
• Primary Examiner(s): Koharski, Christopher D
• Assistant Examiner(s): EDWARDS, PHILIP CHARLES
• Application Number:
  US13/176,484
• Publication Number:
  US 20110263987A1
• Time in Patent Office: 651 Days
• Field of Search: 607/20, 600/484
• US Class Current: 600/484
• CPC Class Codes: A61N 1/3621 for treating or preventing abnormally high heart rate
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence
• CPC Class Codes: A61N 1/3684 for stimulating the heart at multiple sites of the ventricle or the atrium
• CPC Class Codes: A61N 1/36843 Bi-ventricular stimulation
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371

Abstract

An implantable medical device that measures respiration parameters based on transthoracic impedance signals, and converts transthoracic impedance signals into a time series of digital values which is filtered with morphological operators to separate the signal into a respiratory component and a cardiac component. Metrics are generated based on the filtered impedance values such as respiratory rate, I/E ratio, tidal volume and minute ventilation.

Claims

1. A heart monitor configured to obtain respiration metrics comprising:

an impedance signal input;

an impedance measurement unit coupled with said impedance signal input;

a microprocessor configured to obtain a first time series of values that represent a transthoracic impedance signal obtained from said impedance measurement unit; and

,

said microprocessor further configured to

generate a modified time series of values that represent a trend of values of said first time series through application of at least one morphological operator comprising

an erosion operator or

a dilation operator or

any combination thereof

wherein said trend of values comprises a respiratory component of said first times series, and

wherein said at least one morphological operator includes said erosion operator defined by

2. The heart monitor of claim 1, wherein said microprocessor is further configured to subtract said first time series from said modified time series and to thus generate a cardiac component of said first times series.

3. The heart monitor of claim 1, wherein said microprocessor is configured to generate said modified time series through application of both an opening operator and a closing operator to said first time series to thus obtain said modified time series of values that represent the trend of values of said first time series.

4. The heart monitor of claim 3, wherein said microprocessor is configured to generate said modified time series through application of said erosion operator followed by said dilation operator that together form the opening operator to suppress peaks in the first time series.

5. The heart monitor of claim 3, wherein said microprocessor is configured to generate said modified time series through application of said dilation operator followed by said erosion operator that together form the closing operator to suppress pits in the first time series.

6. The heart monitor of claim 1, wherein K is a vector comprising all zeroes.

7. The heart monitor of claim 1, wherein M comprises enough values to cover a time period longer than a cardiac cycle length but shorter than a respiratory cycle length.

8. The heart monitor of claim 1, wherein said trend of values comprises a respiratory component that is measured from a nadir to a following peak to determine inspiration time (TI) and wherein said trend of values is calculated to disregard under-threshold moves in a direction opposite to a current up or down trend of values.

9. The heart monitor of claim 1, wherein said trend of values comprises a respiratory component that is measured from a peak to a following nadir to determine expiration time (TE).

10. The heart monitor of claim 1, wherein said trend of values comprises a respiratory component that is measured by adding time from a nadir to a following peak to a following nadir to determine an instantaneous respiratory cycle length.

11. The heart monitor of claim 10, further comprising calculation of an inverse of instantaneous respiratory cycle length to determine an instantaneous respiratory rate.

12. The heart monitor of claim 10, wherein said trend of values comprises a respiratory component that is measured from a nadir to a following peak to determine inspiration time (TI) and wherein said trend of values comprises another respiratory component that is measured from a peak to a following nadir to determine expiration time (TE) and further comprising calculation of an instantaneous inspiration/expiration ratio or I/E ratio by dividing TI by TE.

13. The heart monitor of claim 1, wherein said trend of values comprises a respiratory component that is measured from a nadir to a following peak to determine an instantaneous tidal volume (TV).

14. The heart monitor of claim 1, wherein said trend of values comprises a respiratory component that is calculated by integration of an area under said trend of values for one minute to determine a minute ventilation.

15. The heart monitor of claim 1, wherein said trend of values is calculated to disregard under-threshold moves, and over-threshold moves in a direction opposite to a current up or down trend of values, such that if a current value of a point in time n is less than, or greater than, a current value at a previous point in time n−

1, and less than, or greater than, a current value at a later in point in time n+1, then the value at point in time n is disregarded as neither a peak or a nadir.

16. A heart monitor configured to obtain respiration metrics comprising:

an impedance signal input;

an impedance measurement unit coupled with said impedance signal input;

a microprocessor configured to obtain a first time series of values that represent a transthoracic impedance signal obtained from said impedance measurement unit;

said microprocessor further configured to generate a modified time series of values that represent a trend of values of said first time series through application of at least one morphological operator wherein said trend of values comprises a respiratory component of said first times series;

wherein said at least one morphological operator includes an erosion operator defined by

17. The heart monitor of claim 16, wherein said trend of values is calculated to disregard under-threshold moves, and over-threshold moves in a direction opposite to a current up or down trend of values, such that if a current value of a point in time n is less than, or greater than, a current value at a previous point in time n−

1, and less than, or greater than, a current value at a later in point in time n+1, then the value at point in time n is disregarded as neither a peak or a nadir.

18. A heart monitor configured to obtain respiration metrics comprising:

an impedance signal input;

an impedance measurement unit coupled with said impedance signal input;

a microprocessor configured to obtain a first time series of values that represent a transthoracic impedance signal obtained from said impedance measurement unit; and

,

said microprocessor further configured to

generate a modified time series of values that represent a trend of values of said first time series through application of at least one morphological operator comprising

an erosion operator or

a dilation operator or

any combination thereof

wherein said trend of values comprises a respiratory component of said first times series;

wherein said trend of values comprises a respiratory component that is measured from a nadir to a following peak to determine inspiration time (TI), and from a peak to following nadir to determine expiration time (TE);

wherein said trend of values is calculated to disregard under-threshold moves, and over-threshold moves in a direction opposite to a current up or down trend of values, such that if a current value of a point in time n is less than, or greater than, a current value at a previous point in time n−

1, and less than, or greater than, a current value at a later in point in time n+1, then the value at point in time n is disregarded as neither a peak or a nadir.