ARTERIAL BLOOD PRESSURE MONITORING DEVICES, SYSTEMS AND METHODS USING CARDIOGENIC IMPEDANCE SIGNAL

• US 20110009754A1
• Filed: 12/14/2009
• Published: 01/13/2011
• Est. Priority Date: 07/08/2009
• Status: Abandoned Application

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Inventors: Hou, Wenbo, Keel, Allen J., Wenzel, Brian Jeffrey, Karst, Edward, Bornzin, Gene A., Farazi, Taraneh Ghaffari
• Application Number:
  US12/637,489
• Publication Number:
  US 20110009754A1
• Time in Patent Office: Days
• US Class Current: 600/485
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: G03F 7/0002 Lithographic processes using patterning methods other than those involving the exposure to radiation, e.g. by stamping

Abstract

Provided herein are implantable systems, and methods for use therewith, for monitoring a patient'"'"'s arterial blood pressure. Electrode(s) implanting within and/or on the patient'"'"'s heart are used to obtain a cardiogenic impedance (CI) signal indicative of cardiac contractile activity. Additionally, a signal (e.g., PPG or IPG signal) indicative of changes in arterial blood volume remote from the patient'"'"'s heart is obtained using a sensor or electrodes that are implanted remote from the patient'"'"'s heart. One or more metrics indicative of pulse arrival time (PAT) are determined, where each metric can be determined by determining a time from one of the detected features of the CI signal to one of the detected features of the signal indicative of changes in arterial blood volume. Based on at least one of the metric(s) indicative of PAT, arterial blood pressure is estimated, which can include determining values indicative of systolic blood pressure, diastolic blood pressure, pulse pressure and/or mean arterial blood pressure, and/or changes in such values.

Claims

1. For use with an implantable system, a method for monitoring a patient'"'"'s arterial blood pressure, the method comprising:

(a) using one or more electrodes implanting within and/or on the patient'"'"'s heart to obtain a cardiogenic impedance (CI) signal indicative of cardiac contractile activity;

(b) using an implanted sensor or implanted electrodes, remote from the patient'"'"'s heart, to obtain a signal indicative of changes in arterial blood volume remote from the patient'"'"'s heart;

(c) detecting one or more predetermined features of the CI signal;

(d) detecting one or more predetermined features of the signal indicative of changes in arterial blood volume remote from the patient'"'"'s heart;

(e) determining one or more metrics indicative of pulse arrival time (PAT), each metric indicative of PAT determined by determining a time from one of the detected features of the CI signal to one of the detected features of the signal indicative of changes in arterial blood volume remote from the patient'"'"'s heart; and

(f) estimating the patient'"'"'s arterial blood pressure based on at least one of the one or more metrics indicative of PAT.

2. The method of claim 1, wherein step (b) comprises one of the following:

using an implanted photoplethysmography sensor, remote from the patient'"'"'s heart, to obtain a photoplethysmography (PPG) signal indicative of changes in arterial blood volume remote from the patient'"'"'s heart; and

using implanted electrodes, remote from the patient'"'"'s heart, to obtain an impedance plethysmography signal (IPG) indicative of changes in arterial blood volume remote from the patient'"'"'s heart.

3. The method of claim 1, wherein step (f) comprises determining a value indicative of systolic blood pressure (SBP) based on at least one of the one or more metrics indicative of PAT.

4. The method of claim 1, wherein step (f) comprises determining a value indicative of diastolic blood pressure (DBP) based on at least one of the one or more metrics indicative of PAT.

5. The method of claim 1, wherein step (f) comprises determining a value indicative of mean arterial blood pressure (MAP) based on at least one of the one or more metrics indicative of PAT.

6. The method of claim 1, wherein step (f) comprises:

determining a value indicative of systolic blood pressure (SBP) based on at least one of the one or more metrics indicative of PAT; and

determining a value indicative of diastolic blood pressure (DBP) based on at least one of the one or more metrics indicative of PAT.

7. The method of claim 6, wherein step (f) further comprises determining a value indicative of mean arterial blood pressure (MAP) based on the value indicative of SBP and the value indicative of DBP.

8. The method of claim 1, wherein the one or more predetermined features of the CI signal detected at step (c) is/are selected from the group consisting of:

minimum amplitude of the CI signal;

maximum upward slope of the CI signal;

maximum amplitude of the CI signal; and

maximum downward slope of the CI signal.

9. The method of claim 1, wherein the signal indicative of changes in arterial blood volume remote from the patient'"'"'s heart obtained at step (b) comprises a photoplethysmography (PPG) signal or an impedance plethysmography (IPG) signal, and the one or more predetermined features of the PPG or IPG signal detected at step (d) is/are selected from the group consisting of:

minimum amplitude of the PPG or IPG signal;

maximum upward slope of the PPG or IPG signal;

maximum amplitude of the PPG or IPG signal;

dicrotic notch of the PPG signal or IPG;

maximum downward slope of the PPG or IPG signal prior to the dicrotic notch; and

maximum downward slope of the PPG or IPG signal following the dicrotic notch.

10. The method of claim 9, wherein step (d) includes:

filtering the PPG or IPG signal to reduce effects of respiratory noise, motion artifacts and baseline drift;

grouping a plurality of cycles of the PPG or IPG signal together and performing an outlier removal process to remove cycles of the PPG or IPG signal that are more than a specified threshold away from a mean of the plurality of cycles of the PPG or IPG signal;

averaging the cycles of PPG or IPG signal remaining after the performance of the outlier removal process to thereby determine an averaged PPG or IPG signal;

determining a first derivative and a second derivative of the averaged PPG or IPG signal; and

detecting, based on the first and second derivatives of the averaged PPG or IPG signal, the one or more predetermined features of the PPG or IPG signal.

11. The method of claim 1, further comprising:

causing paced cardiac events by pacing the patient'"'"'s heart, using implanted electrodes, with a voltage sufficient to cause capture; and

wherein steps (a), (b), (c) and (d) are performed while the patient'"'"'s heart is being paced to cause capture.

12. An implantable system, comprising:

a cardiogenic impedance measurement circuit configured to obtain a cardiogenic impedance (CI) signal indicative of cardiac contractile activity;

a plethysmography sensor configured to obtain a signal indicative of changes in arterial blood volume remote from the patient'"'"'s heart;

an arterial blood pressure monitor configured to

detect one or more predetermined features of the CI signal;

detect one or more predetermined features of the signal indicative of changes in arterial blood volume remote from the patient'"'"'s heart;

determine one or more metrics indicative of pulse arrival time (PAT) based on the detected features of the CI signal and the signal indicative of changes in arterial blood volume remote from the patient'"'"'s heart; and

estimate the patient'"'"'s arterial blood pressure based on at least one of the one or more metrics indicative of PAT.

13. The implantable system of claim 12, wherein the plethysmography sensor is selected from the group consisting of:

a photoplethysmography sensor configured to obtain a photoplethysmography (PPG) signal indicative of changes in arterial blood volume remote from the patient'"'"'s heart; and

circuitry configured to obtain, using electrodes implanted remote from the patient'"'"'s heart, an impedance plethysmography signal (IPG) indicative of changes in arterial blood volume remote from the patient'"'"'s heart.

14. The implantable system of claim 12, wherein the arterial blood pressure monitor is configured to estimate the patient'"'"'s arterial blood pressure by determining one or more values selected from the group consisting of:

a value indicative of systolic blood pressure (SBP) based on at least one of the one or more metrics indicative of PAT;

a value indicative of diastolic blood pressure (DBP) based on at least one of the one or more metrics indicative of PAT;

a value indicative of pulse pressure (PP) based on at least one of the one or more metrics indicative of PAT; and

a value indicative of mean arterial blood pressure (MAP) based on at least one of the one or more metrics indicative of PAT.

15. The implantable system of claim 12, wherein the arterial blood pressure monitor is configured to detect one or more predetermined features of the CI signal selected from the group consisting of:

minimum amplitude of the CI signal;

maximum upward slope of the CI signal;

maximum amplitude of the CI signal; and

maximum downward slope of the CI signal.

16. The implantable system of claim 12, wherein the signal indicative of changes in arterial blood volume remote from the patient'"'"'s heart comprises a photoplethysmography (PPG) signal or an impedance plethysmography (IPG) signal, and wherein the arterial blood pressure monitor is configured to detect one or more predetermined features of the PPG or IPG signal selected from the group consisting of:

minimum amplitude of the PPG or IPG signal;

maximum upward slope of the PPG or IPG signal;

maximum amplitude of the PPG or IPG signal;

dicrotic notch of the PPG signal or IPG;

maximum downward slope of the PPG or IPG signal prior to the dicrotic notch; and

maximum downward slope of the PPG or IPG signal following the dicrotic notch.