Respiration monitoring system based on sensed blood pressure variations

• US 6,506,161 B2
• Filed: 08/10/2001
• Issued: 01/14/2003
• Est. Priority Date: 09/28/1995
• Status: Expired due to Term

• Current Assignee: Data Sciences U K Limited (International Business Machines Corporation)
• Original Assignee: Data Sciences U K Limited (International Business Machines Corporation)
• Inventors: Brockway, Brian P., Brockway, Robert V., Fundakowski, Richard A.
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US09/927,588
• Publication Number:
  US 20020082506A1
• Time in Patent Office: 522 Days
• Field of Search: 600/483-486, 600/490, 600/493, 600/500-502, 600/529, 600/538, 600/543, 600/561, 600/481
• US Class Current: 600/484
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02108 from analysis of pulse wave characteristics
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives

Abstract

A system and method obtains physiologic parameter information of an animal or human, such as respiratory rate, from a blood pressure signal from an implanted blood pressure sensor in the animal or human. Specifically, the blood pressure signal is externally signal processed to develop an amplitude versus time waveform. A sequence of selected blood pressure features derived from individual cardiac cycles of the amplitude versus time waveform over a selected time interval are extracted from the developed amplitude versus time waveform. A mathematical model is fitted to the extracted sequence of selected blood pressure features to yield a fitted mathematical model. The physiologic parameter information is computed from the fitted mathematical model.

Claims

1. A method comprising:

obtaining a time-varying blood pressure signal;

extracting a sequence of blood pressure features from the blood pressure signal, the blood pressure features including one of systolic points and diastolic points;

curve-fitting to the extracted sequence of selected blood pressure features to yield a fitted signal including respiration information; and

obtaining respiration from the fitted signal.

2. The method of claim 1, wherein the curve-fitting uses an n^th order polynominal curve.

3. The method of claim 2, wherein n is at least equal to 3.

4. The method of claim 1, wherein the sequence of blood pressure features corresponds to a sequence of cardiac cycles.

5. The method of claim 1, wherein the extracted sequence of blood pressure features, used by the curve-fitting, is substantially equal-spaced in time.

6. The method of claim 1, wherein the obtaining respiration information comprises computing an indicator of at least one of respiration rate and respiration volume based on at least one of peak values, trough values, and zero-crossings of the fitted signal.

7. The method of claim 1, in which obtaining the time-varying blood pressure signal is performed within a human or animal, and further including transmitting a responsive signal carrying blood pressure information from the human or animal for performing the extracting the sequence of blood pressure features, the curve-fitting to the extracted sequence of blood pressure features, and the obtaining respiration information from the fitted signal.

8. The method of claim 7, further comprising implanting a blood pressure sensor in the human or animal.

9. The method of claim 1, in which at least one of the extracting the sequence of blood pressure features, the curve-fitting to the extracted sequence of blood pressure features, and the obtaining respiration information from the fitted signal includes digital processing of a signal.

10. The method of claim 1, in which the obtaining respiration information includes performing spectral analysis on the fitted signal.

11. An system including:

a blood pressure signal input, receiving a blood pressure signal;

a peak detector, configured to extracting a sequence of blood pressure features from the blood pressure signal, the blood pressure features including one of systolic points and diastolic points;

a curve-fitting module, configured curve-fit to the extracted sequence of selected blood pressure features to yield a fitted signal including respiration information; and

a feature detector, including at least one of a peak detector and a zero-cross detector, configured to obtain respiration information from the fitted signal.

12. The system of claim 11, in which the curve-fitting module includes an n^th order polynomial curve.

13. The system of claim 12, wherein n is at least equal to 3.

14. The system of claim 11, further including a time difference circuit, coupled to an output of at least one of the peak detector and the zero-cross detector, to determine a respiration period therefrom.

15. The system of claim 11, further comprising a blood pressure sensor.

16. The system of claim 15, further comprising a transmitter, coupled to an output of the blood pressure sensor, configured to transmit a signal including blood pressure information from within a human or animal.

17. The system of claim 16, further including a receiver, configured to be communicatively coupled to the transmitter to receive the transmitted signal including blood pressure information.

18. The system of claim 11, including a digital signal processor that includes at least one of the peak detector, the curve-fitting module, and the feature detector.

19. The system of claim 11, in which the feature detector includes a spectral analyzer for performing spectral analysis on the fitted signal.