PLETHYSMOGRAPH VARIABILITY PROCESSOR

• US 20130296713A1
• Filed: 04/08/2013
• Published: 11/07/2013
• Est. Priority Date: 12/09/2006
• Status: Active Grant

• Current Assignee: Masimo Corporation
• Original Assignee: Masimo Corporation
• Inventors: Al-Ali, Ammar, Weber, Walter, Majmudar, Anmol
• Granted Patent: US 10,092,200 B2
• Time in Patent Office: Days
• US Class Current: 600/479
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• 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 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/4848 Monitoring or testing the effects of treatment, e.g. of medication
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

A plethysmograph variability processor inputs a plethysmograph waveform having pulses corresponding to pulsatile blood flow within a tissue site. The processor derives plethysmograph values based upon selected plethysmograph features, determines variability values, and calculates a plethysmograph variability parameter. The variability values indicate the variability of the plethysmograph features. The plethysmograph variability parameter is representative of the variability values and provides a useful indication of various physiological conditions and the efficacy of treatment for those conditions.

Claims

1. A plethysmograph variability method comprising:

receiving a plethysmograph waveform having pulses corresponding to pulsatile blood flow within a tissue site;

determining a plurality of perfusion values corresponding to the pulses, wherein determining the plurality of perfusion values comprises;

identifying peaks and valleys of the pulses, and

calculating differential values for the pulses from the peaks and the valleys of the pulses;

determining a plurality of variability values each indicative of the variability of a series of the perfusion values, wherein determining a variability value of the plurality of variability values includes calculating a difference between a first perfusion value of a series of perfusion values and a second perfusion value of the series of perfusion values;

determining a plethysmograph variability parameter representative of the plurality of variability values; and

causing a display device to display the plethysmograph variability parameter.

2. The method of claim 1, wherein determining the plurality of perfusion values further comprises normalizing the calculated differential values.

3. The method of claim 2, wherein determining the variability value of the plurality of variability values further comprises normalizing the difference between the first perfusion value and the second perfusion value.

4. The method of claim 1, wherein determining the plurality of variability values comprises:

accumulating the plurality of perfusion values in a plurality of buffers, each buffer comprising at least one of the series of perfusion values; and

calculating at least one variability value of the plurality of variability values for each of the buffers.

5. The method of claim 4, wherein determining the plurality of variability values further comprises:

sorting the plurality of perfusion values within each of the buffers from a largest perfusion value to a smallest perfusion value; and

removing at least one perfusion value from a set of largest perfusion values and at least one perfusion value from a set of smallest perfusion values from each of the buffers.

6. The method of claim 4, wherein determining the plurality of variability values further comprises calculating a plurality of plethysmograph variability indices from a percentage difference between a maximum perfusion value and a minimum perfusion value for each of the buffers.

7. The method of claim 6, wherein determining a plethysmograph variability parameter comprises calculating a median value of the plurality of plethysmograph variability indices.

8. The method of claim 7, further comprising:

identifying physiologically acceptable pulses from the pulses, wherein the pulses comprise physiologically acceptable pulses and physiologically unacceptable pulses; and

determining a minimum amount of time of acceptable data in each of the buffers.

9. The method of claim 8, further comprising:

verifying the physiologically acceptable pulses using a red channel,

wherein receiving the plethysmograph waveform comprises using an IR channel for the plethysmograph waveform.

10. A plethysmograph variability system comprising:

a processor in communication with one or more sensors that detect optical radiation after attenuation by pulsatile blood flowing within a tissue site, the processor configured to execute one or more instructions that cause the processor to;

determine a plurality of perfusion values of pulses corresponding to the pulsatile blood flowing within the tissue site, wherein to determine the plurality of perfusion values the processor is further configured to;

identify peaks and valleys of the pulses, and

calculate differential values for the pulses from the peaks and the valleys of the pulses;

determine a plurality of variability values indicative of the variability of a plurality of series of perfusion values, wherein to determine a variability value of the plurality of variability values the processor is further configured to calculate a difference between a first perfusion value of a series of perfusion values and a second perfusion value of the series of perfusion values;

determine a plethysmograph variability parameter representative of the plurality of variability values; and

cause a display to display the plethysmograph variability parameter.

11. The system of claim 10, wherein to determine the plurality of perfusion values, the processor is further configured to normalize the calculated differential values.

12. The system of claim 11, wherein to determine the variability value of the plurality of variability values, the processor is further configured to normalize the difference between the first perfusion value and the second perfusion value.

13. The system of claim 10, wherein to determine the plurality of variability values, the processor is configured to:

store the plurality of perfusion values in a plurality of buffers, each buffer comprising at least one of the series of perfusion values; and

calculate at least one variability value of the plurality of variability values for each of the buffers.

14. The system of claim 13, wherein to determine the plurality of variability values, the processor is configured to:

sort the plurality of perfusion values within each of the buffers from a largest perfusion value to a smallest perfusion value; and

remove at least one perfusion value from a set of largest perfusion values and at least one perfusion value from a set of smallest perfusion values from each of the buffers.

15. The system of claim 13, wherein to determine the plurality of variability values, the processor is further configured to calculate a plurality of plethysmograph variability indices from a percentage difference between a maximum perfusion value and a minimum perfusion value for each of the buffers.

16. The system of claim 15, wherein to determine a plethysmograph variability parameter the processor is configured to calculate a median value of the plurality of plethysmograph variability indices.

17. The system of claim 16, wherein the processor is further configured to:

identify physiologically acceptable pulses from the pulses, wherein the pulses comprise physiologically acceptable pulses and physiologically unacceptable pulses; and

determine a minimum amount of time of acceptable data in each of the buffers.

18. A method for determining a plethysmograph variability parameter, the method comprising:

receiving a plethysmograph waveform having pulses corresponding to pulsatile blood flow within a tissue site;

identifying relative minimums and relative maximums of the pulses;

calculating differential values for the pulses from the identified relative minimums and relative maximums of the pulses to determine a plurality of perfusion values for the pulses, wherein the plurality of perfusion values comprise at least a first set of perfusion values and a second set of perfusion values;

calculating a variability value of the first set of perfusion values using at least a difference between a first perfusion value of the first set of perfusion values and a second perfusion value of the first set of perfusion values;

calculating a variability value of the second set of perfusion values using at least a difference between a first perfusion value of the second set of perfusion values and a second perfusion value of the second set of perfusion values;

determining a plethysmograph variability parameter representative of at least the variability value of the first set of perfusion values and the variability value of the second set of perfusion values; and

causing a display device to display the plethysmograph variability parameter.

19. The method of claim 18, further comprising normalizing the calculated differential values to determine the plurality of perfusion values.

20. The method of claim 19, wherein calculating the variability value of the first set of perfusion values further comprises normalizing the difference between the first perfusion value of the first set of perfusion values and the second perfusion value of the first set of perfusion values.