Multiple wavelength sensor equalization

• US 20060211923A1
• Filed: 03/01/2006
• Published: 09/21/2006
• Est. Priority Date: 03/01/2005
• Status: Active Grant

• Current Assignee: Cercacor Laboratories
• Original Assignee: Masimo Laboratories, Inc. (Masimo Corporation)
• Inventors: Coffin, James P., Abdul-Hafiz, Yassir, Lamego, Marcelo, Al-Ali, Ammar, Diab, Mohamed
• Granted Patent: US 7,647,083 B2
• Time in Patent Office: Days
• US Class Current: 600/310
• CPC Class Codes: A61B 1/00 Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes examination of body cavities or body tracts using ultrasonic, sonic or infrasonic waves A61B8/12; endoscopic instruments for taking cell samples or for biopsy A61B10/04; for surgical purposes A61B17/00; endoscopic surgical cutting instruments A61B17/32; surgical instruments using a laser beam being directed along or through a flexible conduit A61B18/22; Illuminating arrangements therefor for the eyes A61B3/00
• CPC Class Codes: A61B 2562/08 Sensors provided with means for identification, e.g. barcodes or memory chips
• CPC Class Codes: A61B 2562/085 combined with means for recording calibration data
• CPC Class Codes: A61B 2562/185 Optical shielding, e.g. baffles
• CPC Class Codes: A61B 2562/222 Electrical cables or leads therefor, e.g. coaxial cables or ribbon cables
• CPC Class Codes: A61B 5/0022 Monitoring a patient using a global network, e.g. telephone networks, internet
• 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 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/02427 Details of sensor
• 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 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• 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 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: A61B 5/6815 Ear
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6829 Foot or ankle
• CPC Class Codes: A61B 5/6832 : using adhesives A61B5/259 takes precedence
• CPC Class Codes: A61B 5/6838 : Clamps or clips
• CPC Class Codes: A61B 5/7221 : Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/7246 : using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/7275 : Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• 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: A61B 5/7405 : using sound
• CPC Class Codes: A61B 5/742 : using visual displays A61B5/339 takes precedence
• CPC Class Codes: A61B 5/746 : Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B
• CPC Class Codes: A61B 5/7475 : User input or interface means, e.g. keyboard, pointing device, joystick
• CPC Class Codes: G16H 10/40 : for data related to laboratory analysis, e.g. patient specimen analysis
• CPC Class Codes: G16H 40/67 : for remote operation
• CPC Class Codes: H05K 999/99 : dummy group
• CPC Class Codes: Y10S 439/909 : Medical use or attached to human body

Abstract

A physiological sensor has intensity compensation introduced along an optical path from emission to detection so as to compensate for unequal tissue attenuation as a function of wavelength. The sensor has emitters configured to transmit optical radiation having multiple wavelengths into a tissue site. At least one detector is capable of receiving the optical radiation after tissue attenuation. An equalization is capable of compensating optical radiation intensity so as to account for differences in tissue attenuation across at least a portion of the multiple wavelengths.

Claims

1. A physiological sensor having optical intensity compensation introduced along an optical path from emission to detection so as to compensate for unequal tissue attenuation as a function of wavelength, the sensor comprising:

a plurality of emitters configured to transmit optical radiation having a plurality of wavelengths into a tissue site;

at least one detector capable of receiving the optical radiation after tissue attenuation; and

an equalization capable of compensating optical radiation intensity so as to account for differences in tissue attenuation across at least a portion of the plurality of wavelengths.

2. The physiological sensor according to claim 1 wherein the equalization comprises an optical filter having a transfer function adapted to attenuate only selected wavelengths of the optical radiation.

7. The physiological sensor according to claim 1 wherein the emitters comprise at least two emitters having the same one of the wavelengths and capable of simultaneous activation so as to compensate for greater tissue attenuation at that wavelength compared with others of the wavelengths.

8. The physiological sensor according to claim 1 wherein the at least one of the detector has a response as a function of wavelength adapted to compensate for tissue attenuation as a function of wavelength.

9. The physiological sensor according to claim 8 wherein the at least one detector has a response that is more sensitive to red wavelengths compared with IR wavelengths.

3. The physiological sensor according to claim 3 wherein the optical filter is positioned proximate the emitters.

4. The physiological sensor according to claim 3 wherein the optical filter is positioned proximate the at least one detector.

5. The physiological sensor according to claim 3 wherein a subset of the emitters having IR wavelengths are encapsulated with a filtering medium.

6. The physiological sensor according to claim 5 wherein the emitters of the subset are individually encapsulated.

10. A physiological sensor method comprising:

emitting optical radiation having a plurality of wavelengths;

detecting the optical radiation after the tissue attenuation; and

transmitting the optical radiation through a medium,

wherein at least one of the emitting, detecting and transmitting steps is adapted to at least partially reduce wavelength dependence of the tissue attenuation.

11. The physiological sensor method according to claim 10 wherein the emitting comprises:

providing more than one light emitter of the same wavelength; and

activating the more than one light emitter simultaneously.

12. The physiological sensor method according to claim 10 wherein the transmitting comprises selectively filtering the optical radiation with the medium.

13. The physiological sensor method according to claim 10 wherein the filtering comprises encapsulating at least one of emitters with the filtering medium.

14. The physiological sensor method according to claim 13 wherein the filtering medium attenuates at least a portion of emitted IR wavelengths.

15. The physiological sensor method according to claim 10 wherein the detecting comprises utilizing at least one detector having a wavelength dependent response that is generally opposite the wavelength dependent tissue attenuation.

16. The physiological sensor method according to claim 15 wherein the at least one detector response is more sensitive to red wavelengths than to IR wavelengths.

17. A physiological sensor comprising:

an emitter means for emitting optical radiation having a plurality of wavelengths into a tissue site;

a detector means for detecting the optical radiation after tissue attenuation; and

an equalization means for compensating the optical radiation intensity so as to account for differences in tissue attenuation of the optical radiation across at least a portion of the plurality of wavelengths.

18. The physiological sensor according to claim 17 wherein the equalization means is a means for simultaneously activating more than one emitter having the same wavelength.

19. The physiological sensor according to claim 17 wherein the equalization means is an optical filter means for attenuating optical radiation intensity at selected wavelengths.

20. The physiological sensor according to claim 17 wherein the equalization means is a means for utilizing a detector response that is generally opposite the tissue attenuation as a function of wavelength.