Adjusting parameters used in pulse oximetry analysis

• US 9,131,879 B2
• Filed: 07/12/2012
• Issued: 09/15/2015
• Est. Priority Date: 10/28/2005
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Baker, Clark R. Jr.
• Primary Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US13/548,021
• Publication Number:
  US 20120283533A1
• Time in Patent Office: 1,160 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence

Abstract

Adjusting a pulse qualification criterion includes receiving a signal representing a plurality of pulses, where the signal is generated in response to detecting light scattered from blood perfused tissue. A characteristic is determined. A pulse qualification criterion used for qualifying a pulse is adjusted in accordance with the characteristic. The pulses are evaluated according to the pulse qualification criterion.

Claims

1. A method for calculating a physiological parameter, comprising:

receiving, via a processor, a signal representing a plurality of pulses, the signal generated in response to detecting light scattered from blood perfused tissue, each pulse having an amplitude and a period, a subset of the plurality of pulses having a plurality of amplitudes and a plurality of periods;

determining, via the processor, an average amplitude from the plurality of amplitudes;

determining, via the processor, an average period from the plurality of periods;

adjusting, via the processor, an amplitude criterion based on the average amplitude and a period criterion based on the average period;

evaluating, via the processor, one or more of the plurality of pulses to determine one or more qualified pulses by disqualifying a pulse having an amplitude that is smaller than the amplitude criterion and a period that is greater that the period criterion;

ensemble averaging, via an ensemble averaging filter, the one or more qualified pulses;

calculating, via the processor, a physiological parameter based at least in part upon one or more ensemble averaged pulses; and

outputting, via the processor, the physiological parameter for display.

2. The method of claim 1, wherein evaluating one or more of the plurality of pulses comprises:

disqualifying a pulse having an amplitude that is more than three times smaller than the amplitude criterion.

3. The method of claim 1, comprising determining, via the processor, a ratio-of-ratios variance for the one or more ensemble averaged pulses and calculating, via the processor, oxygen saturation based at least in part on the one or more ensemble averaged pulses and the ratio-of-ratios variance.

4. The method of claim 3, comprising determining, via the processor, a saturation weight based at least in part upon the ratio-of-ratios variance and a response mode, and wherein calculating oxygen saturation comprises calculating oxygen saturation based on the saturation weight.

5. A system configured to calculate a physiological parameter, comprising:

an interface configured to;

receive a signal representing a plurality of pulses, the signal generated in response to detecting light scattered from blood perfused tissue, each pulse having an amplitude and a period, a subset of the plurality of pulses having a plurality of amplitudes and a plurality of periods;

an ensemble averaging filter configured to filter the signal;

a processor configured to;

determine an average amplitude from the plurality of amplitudes;

determine an average period from the plurality of periods;

adjust an amplitude criterion based on the average amplitude and a period criterion based on the average period; and

evaluate one or more of the plurality of pulses to determine one or more qualified pulses by disqualifying a pulse having an amplitude that is smaller than the amplitude criterion and a period that is greater that the period criterion;

wherein the ensemble averaging filter is configured to ensemble average the one or more qualified pulses, and the processor is configured to calculate a physiological parameter based at least in part upon one or more ensemble averaged pulses and output the physiological parameter for display.

6. The system of claim 5, the processor further configured to evaluate one or more of the plurality of pulses by:

disqualifying a pulse when a ratio of a period of the pulse relative to the average period is greater than a threshold.

7. The system of claim 5, wherein the processor is configured to evaluate one or more of the plurality of pulses to determine the one or more qualified pulses using a trained neural net.

8. The system of claim 5, wherein the processor is configured to determine a ratio-of-ratios variance for the one or more ensemble averaged pulses and calculate oxygen saturation based at least in part on the one or more ensemble averaged pulses and the ratio-of-ratios variance.

9. The system of claim 8, wherein the processor is configured to determine a saturation weight based at least in part upon the ratio-of-ratios variance and a response mode, and the processor is configured to calculate oxygen saturation based on the saturation weight.

10. A system for calculating a physiological parameter, comprising:

means for receiving a signal representing a plurality of pulses, the signal generated in response to detecting light scattered from blood perfused tissue, each pulse having an amplitude and a period, a subset of the plurality of pulses having a plurality of amplitudes and a plurality of periods;

means for determining an average amplitude from the plurality of amplitudes;

means for determining an average period from the plurality of periods;

means for adjusting an amplitude criterion based on the average amplitude and a period criterion based on the average period; and

means for evaluating one or more of the plurality of pulses to determine one or more qualified pulses by disqualifying a pulse having an amplitude that is smaller than the amplitude criterion and a period that is greater that the period criterion;

means for ensemble averaging the one or more qualified pulses;

means for calculating a physiological parameter based on one or more ensemble averaged pulses; and

means for outputting the physiological parameter for display.

11. The system of claim 10, comprising:

means for determining a ratio-of-ratios variance for the one or more ensemble averaged pulses;

means for calculating oxygen saturation based at least in part on the one or more ensemble averaged pulses and the ratio-of-ratios variance.

12. The system of claim 11, comprising means for determining a saturation weight based at least in part upon the ratio-of-ratios variance and a response mode, and wherein calculating oxygen saturation comprises calculating oxygen saturation based on the saturation weight.

13. An system configured to calculate a physiological parameter, comprising:

an interface configured to;

receive a signal representing a plurality of pulses, the signal generated in response to detecting light scattered from blood perfused tissue, each pulse having an amplitude and a period, a subset of the plurality of pulses having a plurality of amplitudes and a plurality of periods;

an ensemble averaging filter configured to filter the signal;

a processor configured to;

determine an average amplitude from the plurality of amplitudes;

determine an average period from the plurality of periods;

adjust an amplitude criterion based on the average amplitude and a period criterion based on the average period; and

evaluate one or more of the plurality of pulses to determine one or more qualified pulses by;

disqualifying a pulse having an amplitude that is more than three times smaller than the amplitude criterion and a period that is greater that the period criterion;

wherein the ensemble averaging filter is configured to ensemble average the one or more qualified pulses, and the processor is configured to calculate a physiological parameter based at least in part on one or more ensemble averaged pulses and to output the physiological parameter for display.

14. The system of claim 13, wherein the processor is configured to determine a ratio-of-ratios variance for the one or more ensemble averaged pulses and calculate oxygen saturation based at least in part on the one or more ensemble averaged pulses and the ratio-of-ratios variance.

15. The system of claim 14, wherein the processor is configured to determine a saturation weight based at least in part upon the ratio-of-ratios variance and a response mode, and the processor is configured to calculate oxygen saturation based on the saturation weight.