Physiological parameter tracking system

• US 20050090724A1
• Filed: 08/30/2004
• Published: 04/28/2005
• Est. Priority Date: 08/28/2003
• Status: Active Grant

• Current Assignee: Masimo Corporation
• Original Assignee: Masimo Corporation
• Inventors: Weber, Walter M., Al-Ali, Ammar, Diab, Mohamed
• Granted Patent: US 7,254,431 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 2560/0204 of power management
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/72 Signal processing specially adapted for physiological signals or for diagnostic purposes character recognition, recognising digital ink, document-oriented image-based pattern recognition G06V30/00; recognition or understanding of postal images G06V30/424

Abstract

A physiological parameter tracking system generates a reference parameter and a slowly varying parameter responsive to a physiological signal input. The slowly varying parameter is generated according to an update command. A physiological measurement output is provided that is responsive to a tracking function of the reference parameter and the slowly varying parameter.

Claims

1. A physiological parameter tracking system comprising:

a physiological signal input having at least first and second intensity signal components received from a light-sensitive detector that detects light of at least first and second wavelengths transmitted through body tissue carrying pulsing blood, wherein the first and second intensity signal components are at least partially based on a pulse of the pulsing blood;

a reference parameter responsive to said physiological signal;

an update command;

a slow parameter responsive to said physiological signal according to said update command;

a tracking function responsive to said reference parameter and said slow parameter; and

a physiological measurement output responsive to said tracking function.

2. The physiological parameter tracking system according to claim 1 further comprising an ancillary parameter responsive to said physiological signal, wherein said slow parameter is responsive to a slow parameter function of said reference parameter and said ancillary parameter.

3. The physiological parameter tracking system according to claim 2 further comprising an output multiplexer configured so that said physiological measurement is responsive to one of said tracking function output and said ancillary parameter according to said update command.

4. The physiological parameter tracking system according to claim 1 wherein said slow parameter is a measure of abnormal hemoglobin, said reference parameter is a measure of oxygen saturation and said physiological measurement is indicative of oxygen saturation corrected for abnormal hemoglobin.

5. The physiological parameter tracking system according to claim 2 wherein said ancillary parameter is a measure of venous oxygen saturation, said reference parameter is a measure of arterial oxygen saturation, said slow parameter is a measure of oxygen consumption and said physiological measurement is indicative of venous oxygen saturation.

6. The physiological parameter tracking system according to claim 1 wherein said update command operates in at least one of a sample and hold mode and a track and hold mode.

7. The physiological parameter tracking system according to claim 1 wherein said tracking function output is responsive to a difference between said reference parameter and said slow parameter.

8. A physiological parameter tracking method comprising the steps of:

inputting a physiological signal;

calculating a reference parameter from said signal;

defining an update command;

tracking said reference parameter according to said update command; and

outputting a physiological measurement responsive to said tracking step.

9. The physiological parameter tracking method according to claim 8 wherein said defining step comprises the substeps of:

indicating one of a sample period and a tracking period for calculating a slow parameter response to said signal; and

indicating a hold period for maintaining a previous calculation of said slow parameter.

10. The physiological parameter tracking method according to claim 9 wherein said tracking step comprises the substep of deriving a tracking function output from said reference parameter and said slow parameter.

11. The physiological parameter tracking method according to claim 10 further comprising the step of calculating an ancillary parameter from said signal.

12. The physiological parameter tracking method according to claim 11 wherein said outputting step comprises the substep of multiplexing said tracking function output and said ancillary parameter according to said update command.

13. The physiological parameter tracking method according to claim 12 wherein said ancillary parameter is venous oxygen saturation and said physiological measurement is said venous oxygen saturation during said tracking period and an estimate of venous oxygen saturation during said hold period.

14. The physiological parameter tracking method according to claim 11 wherein said ancillary parameter is a measure of abnormal hemoglobin.

15. The physiological parameter tracking method according to claim 14 wherein said physiological measurement is arterial oxygen saturation corrected for said abnormal hemoglobin.

16. A physiological parameter tracking method comprising the steps of:

providing a physiological signal;

calculating arterial oxygen saturation from said signal;

calculating a slowly varying parameter during a first period;

holding said slowly varying parameter during a second period; and

outputting a physiological measurement responsive to said arterial oxygen saturation and said slowly varying parameter.

17. The physiological parameter tracking method according to claim 16 wherein said slowly varying parameter is abnormal hemoglobin concentration and said physiological measurement is said arterial oxygen saturation corrected for said abnormal hemoglobin concentration.

18. The physiological parameter tracking method according to claim 16 wherein said slowly varying parameter is a difference between said arterial oxygen saturation and venous oxygen saturation and said physiological measurement is said venous oxygen saturation during said first period and a venous oxygen saturation estimate during said second period.

19. The physiological parameter tracking method according to claim 16 wherein said calculating a slowly varying parameter step comprises the substeps of:

indicating favorable conditions with an update command; and

sampling said slowly varying parameter in response to said command.

20. The physiological parameter tracking method according to claim 16 wherein said holding step comprises the substeps of:

indicating unfavorable conditions with an update command; and

holding said slowly varying parameter in response to said command.