Apparatus and method for monitoring respiration with a pulse oximeter

• US 20030163033A1
• Filed: 02/22/2002
• Published: 08/28/2003
• Est. Priority Date: 02/22/2002
• Status: Active Grant

• Current Assignee: Datex-Ohmeda Incorporated (General Electric Company)
• Original Assignee: Datex-Ohmeda Incorporated (General Electric Company)
• Inventors: Dekker, Andreas Lubbertus Aloysius Johannes
• Granted Patent: US 6,709,402 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips

Abstract

An apparatus and method for monitoring a secondary physiological process through variations caused by the secondary process in an optical signal used to calculate values related to blood oxygen levels. In particular, the optical signal may be divided into distinct portions such that a portion more directly affected by a particular secondary physiological process may be isolated and the secondary physiological process monitored. The apparatus and method is particularly useful for photoplethysmographically monitoring a patient'"'"'s respiration frequency through changes in relative concentrations of blood oxygen related values that are proportionally related to the amounts of venous and arterial blood in a portion of tissue.

Claims

1. An apparatus for monitoring at least one secondary physiological process through variations caused by said secondary process in a portion of an optical signal used to calculate values related to blood oxygen levels, said apparatus comprising:

at least a first emitter for controllably emitting at least first and second wavelengths of electromagnetic radiation to a portion of living tissue;

a detector for detecting signals relative to said transmitted first and second wavelengths of electromagnetic radiation and producing a detector signal indicative thereof; and

a processor operative to;

produce a first output relating to said blood oxygen levels through mathematical computation using at least a first portion of said detector signal for each said wavelength;

monitor said first output over a predetermined period of time to identify variations in said first output indicative of said secondary physiological process; and

generate a second output indicative of said secondary physiological process.

2. The apparatus of claim 1, wherein said secondary physiological process is a process related to operation of the cardiopulmonary system.

3. The apparatus of claim 2, wherein said cardiopulmonary process relates to the respiratory process.

4. The apparatus of claim 3, wherein said process related to the respiratory system comprises one of inspiration and expiration.

5. The apparatus of claim 1, wherein said first output is the ratio of oxyhemoglobin to de-oxyhemoglobin of said tissue.

6. The apparatus of claim 1, wherein said at least a first emitter comprises at least a first light emitting diode.

7. The apparatus of claim 6, further comprising a first and second light emitting diode for emitting electromagnetic radiation in the visible and infrared range respectively.

8. The apparatus of claim 1, wherein said detector comprises a photodetector which produces said detector signal wherein said detector signal comprise an AC component and a DC component.

9. The apparatus of claim 1, wherein said processor produces an output relating to said first physiological parameter using one of said AC and DC components of said detector signal.

10. The apparatus of claim 1, wherein said processor includes a pulse oximeter means to determine an oxygen saturation value related to the ratio of arterial blood to venous blood in said tissue.

12. The apparatus of claim 1, wherein said processor monitors said first output for variations over a frequency range of 0 to 1.5 hertz.

11. The apparatus of claim 11, wherein said processor monitors said value for variations

13. A method for monitoring at least one secondary physiological process based on variations caused by said secondary process in at least a portion of an optical signal used to calculate values related to blood oxygen levels, said method comprising the steps of:

applying electromagnetic radiation of at least of one known wavelength to a portion of tissue;

detecting signals relative to said at least one wavelength of electromagnetic radiation applied to said portion of tissue;

generating a signal indicative of said detected radiation;

processing said generated signal for using at least a first portion of each said generated signal such that an output related with said blood oxygen levels is produced;

monitoring said output over a predetermined time period for variations indicative of said secondary physiological process; and

generating a signal indicative of said secondary physiological process.

14. The method of claim 13, wherein said processing step produces an output related to the ratio of arterial blood to venous blood in said portion of tissue, wherein said ratio is related to blood oxygen levels.

15. The method of claim 14, wherein said monitoring step further comprises monitoring said ratio of arterial blood to venous blood over a predetermined interval to determine said secondary physiological process.

16. The method of claim 15, wherein said secondary process is a respiratory process.

17. The method of claim 15, wherein said predetermined interval is between 0 and 1.5 hertz.

18. A method for monitoring a patient'"'"'s respiration through changes in the patient'"'"'s blood concentrations, said method comprising the steps of:

monitoring a portion of perfused tissue to determine changes in a relative concentration of venous and arterial blood contained therein; and

based on said step of monitoring said relative concentrations of arterial and venous blood, determining a respiration frequency from increases and decreases in said relative concentration.

19. The method of claim 18, wherein said step of monitoring said relative concentration of venous and arterial blood is performed non-invasively.

20. The method of claim 19, wherein said step of non-invasively monitoring is performed photoplethysmographically.

21. The method of claim 20, wherein said step of photoplethysmographically monitoring further comprises the steps of:

applying electromagnetic radiation of one or more known wavelengths to said portion of tissue;

detecting signals relative to said one or more wavelengths of electromagnetic radiation for each said wavelength applied to said portion of tissue;

generating a signal indicative of said detected radiation;

processing at least one portion of said generated signal such that a first blood oxygen related value proportional to venous blood is produced and a second blood oxygen related value proportional to arterial blood is produced; and

monitoring said first and second values over a predetermined time period for variations.

22. An apparatus for monitoring respiration, using optical signals to identify changes in values related to blood oxygen levels caused by said respiration, said apparatus comprising:

at least a first emitter for controllably emitting at least first and second wavelengths of electromagnetic radiation to a portion of living tissue;

a detector for detecting signals relative to said emitted first and second wavelengths of said electromagnetic radiation and producing a detector signal indicative thereof; and

a processor operable to receiving said filtered signals, said processor further operable to;

filter said detector signal such that portions of said signals are isolated; and

determine a value related to blood oxygen levels of said tissue through a mathematical computation using at least a first portion of said filtered signal;

monitor said value to determine variations in said value over a predetermined frequency range indicative of respiration; and

generate an output signal indicative of said respiration.

23. The apparatus of claim 22, wherein said at least a first emitter comprises at least a first light emitting diode.

24. The apparatus of claim 23, further comprising a first and second light emitting diode for emitting electromagnetic radiation in the visible and infrared range respectively.

25. The apparatus of claim 22, wherein said detector comprises a photodetector which produces a multiplexed detector containing a component for each said wavelength wherein each said wavelength further comprises an AC and DC component.

26. The apparatus of claim 25, wherein said at least a first emitter and said detector or contained in a plethysmographic sensor.

27. The apparatus of claim 25, wherein said filter removes one of said AC and DC components of said detector signal.

28. The apparatus of claim 25, wherein said processor determines a value related to an oxygen saturation value from one of said AC and DC components of said filtered signals related to the ratio of arterial blood to venous blood in said tissue.

29. The apparatus of claim 22, wherein said processor monitors said oxygen saturation values over a predetermined time cycle for changes in said value indicative of respiration.

30. The apparatus of claim 29, wherein said predetermined time cycle is from 0 to 1.5 hz.