Plethysmograph pulse recognition processor

• US 20030032873A1
• Filed: 10/08/2002
• Published: 02/13/2003
• Est. Priority Date: 12/30/1998
• Status: Active Grant

• Current Assignee: Mohamed K. Diab
• Original Assignee: Mohamed K. Diab
• Inventors: Diab, Mohamed K.
• Granted Patent: US 6,816,741 B2
• Time in Patent Office: Days
• US Class Current: 600/310
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00

Abstract

An intelligent, rule-based processor provides recognition of individual pulses in a pulse oximeter-derived photo-plethysmograph waveform. Pulse recognition occurs in two stages. The first stage identifies candidate pulses in the plethysmograph waveform. The candidate pulse stage identifies points in the waveform representing peaks and valleys corresponding to an idealized triangular wave model of the waveform pulses. At this stage, waveform features that do not correspond to this model are removed, including the characteristic dicrotic notch. The second stage applies a plethysmograph model to the candidate pulses and decides which pulses satisfies this model. This is done by first calculating certain pulse features and then applying different checks to identify physiologically acceptable features. Various statistics can then be derived from the resulting pulse information, including the period and signal strength of each pulse and pulse density, which is the ratio of the analyzed waveform segment that has been classified as physiologically acceptable.

Claims

1. A processor having a plethysmograph waveform input resulting from light attenuated by body tissue with pulsing blood and a pulse recognition output providing information regarding pulses within said waveform input, said processor comprising:

a candidate pulse portion that determines a plurality of potential pulses within said waveform input; and

a physiological model portion that determines the physiologically acceptable ones of said pulses.

2. The processor of claim 1 further comprising a portion that determines statistics of pulses with said waveform input.

3. The processor of claim 2 wherein one of said statistics is the density of physiologically acceptable pulses within said waveform input.

4. The processor of claim 1 wherein said candidate pulse portion provides an output identifying said potential pulses as the peaks and valleys of a triangular wave.

5. The processor of claim 1 wherein said physiological model portion comprises a component that extracts features of said potential pulses.

6. The processor of claim 5 wherein said features include at least one of pulse period, pulse starting point and pulse signal strength.

7. The processor of claim 1 wherein said physiological model portion comprises a component that disregards ones of said potential pulses having a period below a predetermined threshold.

8. The processor of claim 1 wherein said physiological model portion comprises a component that disregards ones of said potential pulses that are generally asymmetric.

9. The processor of claim 1 wherein said physiological model portion comprises a component that disregards ones of said potential pulses that have a descending trend that is generally slower that a subsequent ascending trend.

10. The processor of claim 1 wherein said physiological model portion comprises a component that disregards ones of said potential pulses that do not sufficiently comply with an empirical relationship between pulse rate and pulse signal strength.

11. The processor of claim 1 wherein said physiological model portion comprises a component that disregards ones of said potential pulses having a signal strength that differs from a short-term average signal strength by greater than a predetermined amount.

12. A method of recognizing pulses within a plethysmograph waveform resulting from light attenuated by body tissue with pulsing blood comprising the steps of:

identifying a plurality of potential pulses in said waveform; and

comparing said potential pulses to a physiological pulse model to derive at least one physiologically acceptable pulse.

13. The method of claim 12 comprising the further step of generating statistics for said at least one acceptable pulse.

14. The method of claim 13 wherein said generating step comprises the steps of:

determining a total period of said at least one acceptable pulse;

calculating the ratio of said total period to a duration of said waveform to derive pulse density.

15. The method of claim 13 where said comparing step comprises the steps of:

extracting pulse features from said potential pulses; and