Plethysmograph pulse recognition processor

• US 6,816,741 B2
• Filed: 10/08/2002
• Issued: 11/09/2004
• Est. Priority Date: 12/30/1998
• Status: Expired due to Term

• Current Assignee: Masimo Corporation
• Original Assignee: Masimo Corporation
• Inventors: Diab, Mohamed K.
• Primary Examiner(s): Jones, Mary Beth
• Assistant Examiner(s): Kremer, Matthew J
• Application Number:
  US10/267,446
• Publication Number:
  US 20030032873A1
• Time in Patent Office: 763 Days
• Field of Search: 600/309-311, 600/322-326, 600/500, 600/330, 600/504, 600/331, 600/336
• US Class Current: 600/324
• 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 capable of analyzing signals received from a light-sensitive detector that detects light having a plurality of wavelengths transmitted through body tissue carrying pulsing blood, the processor comprising:

a first module capable of identifying physiologically acceptable pulses within a plethysmograph waveform comprised of one or more signals received from a light-sensitive detector that detects light having a plurality of wavelengths transmitted through body tissue carrying pulsing blood; and

a second module capable of computing a plurality of statistics regarding said physiologically acceptable pulses identified by said first module,

wherein said first module comprises a component that identifies edges within said plethysmograph waveform, wherein each of said edges comprises a first end point at a peak of said waveform and a second end point at a subsequent valley of said waveform, and wherein said first module comprises a component that disregards ones of said edges that do not cross zero.

2. A processor capable of analyzing signals received from a light-sensitive detector that detects light having a plurality of wavelengths transmitted through body tissue carrying pulsing blood, the processor comprising:

a first module capable of identifying physiologically acceptable pulses within a plethysmograph waveform comprised of one or more signals received from a light-sensitive detector that detects light haying a plurality of wavelengths transmitted through body tissue carrying pulsing blood; and

a second module capable of computing a plurality of statistics regarding said physiologically acceptable pulses identified by said first module,

wherein said first module comprises a component that identifies edges within said plethysmograph waveform, wherein each of said edges comprises a first end point at a peak of said waveform and a second end point at a subsequent valley of said waveform, and wherein said first module comprises a component that determines the maximum value of said waveform between the second end point of a first edge and the first end point of a subsequent second edge and disregards said first edge if said maximum value exceeds a threshold.

3. A processor capable of analyzing signals received from a tight-sensitive detector that detects light having a plurality of wavelengths transmitted through body tissue carrying pulsing blood, the processor comprising:

a first module capable of identifying physiologically acceptable pulses within a plethysmograph waveform comprised of one or more signals received from a light-sensitive detector that detects light having a plurality of wavelengths transmitted through body tissue carrying pulsing blood; and

a second module capable of computing a plurality of statistics regarding said physiologically acceptable pulses identified by said first module,

wherein said first module comprises a component that identifies edges within said plethysmograph waveform, wherein each of said edges comprises a first end point at a peak of said waveform and a second end point at a subsequent valley of said waveform, and wherein said first module comprises a component that generates a triangular waveform with points corresponding to points within said plethysmograph waveform.

4. A device for monitoring physiological parameters of a patient, the device comprising a processor capable of identifying a plurality of potential pulses within a plethysmograph waveform comprised of one or more signals received from a light-sensitive detector that detects light having a plurality of wavelengths transmitted through body tissue carrying pulsing blood, wherein said processor is also capable of identifying a physiologically acceptable pulse from among said plurality of potential pulses by evaluating differences between a segment of said plethysmograph waveform corresponding to a given potential pulse and an approximation of said segment, wherein said processor comprises a component that identifies edges within said plethysmograph waveform, wherein each of said edges comprises a first end point at a peak of said waveform and a second end point at a subsequent valley of said waveform, and wherein said processor comprises a component that determines the maximum value of said waveform between the second end point of a first edge and the first end point of a second subsequent edge and disregards said first edge if said maximum value exceeds a threshold.

5. The device of claim 4, wherein said processor comprises a component that disregards ones of said edges having a distance between said first and second end points that does not fall within a predetermined range.

6. The device of claim 4, wherein said processor comprises a component that disregards ones of said edges that do not cross zero.

7. The device of claim 4, wherein said processor comprises a component that disregards ones of said edges having a second end point that is not below a threshold.

8. The device of claim 4, wherein said processor comprises a component that generates a triangular waveform with points corresponding to points within said plethysmograph waveform.

9. The device of claim 4, wherein said approximation of said plethysmograph waveform segment comprises a stick model of said segment.

10. The device of claim 4, further comprising a multiparameter patient monitor.

11. The device of claim 10, wherein said multiparameter patient monitor comprises a pulse oximeter.

12. The device of claim 11, wherein said processor comprises a component that receives a plurality of inputs comprising potential pulse rates and provides an output comprising a pulse rate, wherein at least one of said plurality of inputs is received from said pulse oximeter.

13. The device of claim 12, wherein said output pulse rate is selected by comparing said inputs and evaluating correlations between said inputs.

14. The device of claim 12, wherein a confidence level is associated with one or more of said inputs and said output pulse rate is selected by evaluating correlations between said inputs and the confidence levels associated with said inputs.

15. The device of claim 12, wherein said output pulse rate comprises an average of two or more of said inputs.

16. The device of claim 12, wherein a confidence level is associated with one or more of said inputs and said output pulse rate comprises an average of two or more of said inputs that is weighted based on the confidence levels associated with said inputs.