Pulse oximeter and method of operation

Abstract

A sensor for use in an optical measurement device and a method for non-invasive measurement of a blood parameter. The sensor includes sensor housing, a source of radiation coupled to the housing, and a detector assembly coupled to the housing. The source of radiation is adapted to emit radiation at predetermined frequencies. The detector assembly is adapted to detect reflected radiation at least one predetermined frequency and to generate respective signals. The signals are used to determine the parameter of the blood.

What is claimed is:  
     
         1 . A sensor for use in an optical measurement device for non-invasive measurement of a blood parameter, the sensor comprising: 
 (a) a light source for illuminating a measurement location with incident light of at least three wavelengths, the first wavelength λ1 lying in a red (R) spectrum, and the at least second and third wavelengths λ2 and λ3 lying substantially in the infrared (IR) spectrum; and    (b) a detector assembly for detecting light returned from the illuminated location, the detector assembly being arranged so as to define a plurality of detection locations along at least one closed path around the light source.    
     
     
         2 . A sensor as set forth in  claim 1 , for use in a pulse oximeter, the at least second and third wavelengths λ2 and λ3 being selected to coincide with a spectral region of the optical absorption curve, where HbO 2  absorbs slightly more light than Hb, and where the extinction coefficients of Hb and HbO 2  are nearly equal and remain relatively constant as a function of wavelength.  
     
     
         3 . A sensor, as set forth in  claim 2 , wherein the second wavelength λ2 is in the IR spectral region around 940 nm+/−20 nm, and the third wavelength λ3 is above 700 nm.  
     
     
         4 . A sensor, as set forth in  claim 1 , wherein the detector assembly comprises at least one array of detector elements arranged in a spaced-apart relationship along the at least one closed path.  
     
     
         5 . A sensor, as set forth in  claim 1 , wherein the detector assembly comprises at least one ring-shaped detector element.  
     
     
         6 . A sensor according to  claim 1 , wherein the plurality of the detection locations are arranged along two concentric closed paths around the light source.  
     
     
         7 . A sensor, as set forth in  claim 6 , wherein the detector assembly comprises two arrays of detector elements, the detector elements of each array being arranged in a spaced apart relationship along the corresponding one of the closed paths.  
     
     
         8 . A sensor, as set forth in  claim 6 , wherein the detector assembly comprises two concentric ring-shaped detector elements.  
     
     
         9 . A sensor, as set forth in  claim 1 , manufactured by CMOS technology, the sensor comprising a package including said light source, and an integrated circuit plate, which comprises said at least one closed path of the detector assembly positioned around the light source, and a plurality of printed contact areas and electric conductors for mounting the light source thereon, controlling the light source, and transmitting electric signals produced by the detector assembly for further processing.  
     
     
         10 . A sensor for use in an optical measurement device for non-invasive measurement of a blood parameter, the sensor comprising: 
 a light source for illuminating a measurement location with incident light of at least three wavelengths, the first wavelength λ1 lying in a red (R) spectrum, and the at least second and third wavelengths λ2 and λ3 lying substantially in the infrared (IR) spectrum; and    a detector assembly for detecting light returned from the illuminated location, the detector assembly being arranged so as to define a plurality of detection locations along two concentric closed path around the light source.    
     
     
         11 . A pulse oximeter comprising a sensor and a control unit for operating the sensor and analyzing data generated thereby, the sensor comprising: 
 (a) a light source for illuminating a measurement location with incident light of at least three wavelengths, the first wavelength λ1 lying in a red (R) spectrum, and the at least second and third wavelengths λ2 and λ3 lying substantially in the infrared (IR) spectrum; and    (b) a detector assembly for detecting light returned from the illuminated location, the detector assembly being arranged so as to define a plurality of detection locations along at least one closed path around the light source.    
     
     
         12 . A method for non-invasive determination of a blood parameter, the method comprising the steps of: 
 (i) illuminating a measurement location with at least three different wavelengths, a first wavelength λ1 lying in a red (R) spectrum, and at least second and third wavelengths λ2 and λ3 lying substantially in the infrared (IR) spectrum;    (ii) detecting light returned from the measurement location at different detection locations and generating data indicative of the detected light, wherein said different detection locations are arranged so as to define at least one closed path around the measurement location; and    (iii) analyzing the generated data and determining the blood parameter.    
     
     
         13 . The method according to  claim 12 , wherein the analysis of the generated data comprises the steps of: 
 calculating data indicative of an AC/DC ratio in the light detected at each of the detection locations for the at least three wavelengths:    analyzing the calculated data and determining accepted detection locations to select corresponding AC/DC ratios for each of the at least three wavelengths, λ1, λ2 and λ3 ;and    utilizing the selected ratios for determining the blood parameter.    
     
     
         14 . The method according to  claim 13 , wherein the determination of the blood parameter comprises the steps of: 
 calculating values of the ratio W 2 /W 3  for the accepted detection locations in at least one closed path;    analyzing each of the calculated values to determine whether it satisfies a first predetermined condition, so as to generate a signal indicative of that a sensor position is to be adjusted, if the condition is not satisfied;    if the condition is satisfied, determining whether the quality of a photoplethysmogram is acceptable;    if the quality is acceptable, analyzing the selected ratios for calculating ratios W 1 /W 2  and W 1 /W 3  from the data detected in at least one closed path, and calculating the differences ABS (W 1 /W 2  −W 1/W   3 ); and,    analyzing the calculated differences for determining whether each of the differences satisfies a second predetermined condition for determining the blood parameter if the condition is satisfied.    
     
     
         15 . The method according to  claim 14 , wherein said first predetermined condition consists of that the calculated value of W 2 /W 3  is inside a predetermined range around the value one, said predetermined range being defined by the first threshold value, and the second predetermined condition consists of that the calculated difference ABS (W 1 /W 2  −W 1 /W 3 ) is less than certain, second threshold value.  
     
     
         16 . A pulse oximeter for detecting a value of a parameter of blood, comprising: 
 a sensor housing;    a source of radiation coupled to the housing and being adapted to emit radiation at predetermined frequencies;    a detector assembly coupled to the housing and being adapted to detect reflected radiation at first, second, and third frequencies and to generate respective first, second, and third signals, wherein the first, second, and third signals are indicative of a value of the reflected radiation at the respective first, second, and third frequencies; and,    a control unit coupled to the detector assembly and adapted to receive the first, second, and third signals, to calculate first, second and third ratios of the first, second, and third signals and to responsively determine the parameter of the blood as a function of the first, second and third ratios.    
     
     
         17 . A pulse oximeter, as set forth in  claim 16 , wherein the control unit is adapted to determine the parameter of the blood as a function of the first and second ratios and a calibration curve.  
     
     
         18 . A pulse oximeter, as set forth in  claim 17 , wherein the calibration curve is adjusted as a function of the third ratio.  
     
     
         19 . A pulse oximeter, as set forth in  claim 16 , wherein the first ratio is defined by the first signal divided by the second signal.  
     
     
         20 . A pulse oximeter, as set forth in  claim 16 , wherein the second ratio is defined by the first signal divided by the third signal.  
     
     
         21 . A pulse oximeter, as set forth in  claim 16 , wherein the third ratio is defined by the second signal divided by the third signal.  
     
     
         22 . A pulse oximeter, as set forth in  claim 16 , wherein the first frequency is in a red frequency range, the second frequency is in a near-infrared frequency range, and the third frequency is in an infrared frequency range.  
     
     
         23 . A pulse oximeter, as set forth in  claim 22 , wherein the first ratio is defined by the first signal divided by the second signal, the second ratio is defined by the first signal divided by the third signal, and the third ratio is defined by the second signal divided by the third signal.  
     
     
         24 . A pulse oximeter, as set forth in  claim 16 , wherein the control unit is adapted to determine the parameter of the blood as a function of a more stable one of the first and second ratios.  
     
     
         25 . A pulse oximeter for detecting a value of a arameter of blood, comprising: 
 a sensor housing;    a source of radiation coupled to the housing and being adapted to emit radiation at predetermined frequencies;    a detector assembly coupled to the housing and being adapted to detect reflected radiation at first, second, and third frequencies and to generate respective first, second, and third signals, wherein the first, second, and third signals are indicative of a value of the reflected radiation at the respective first, second, and third frequencies; and,    a control unit coupled to the detector assembly and being adapted to calculate first and second ratios of the first, second, and third signals, wherein the first ratio is defined by the first signal divided by the second signal and the second ratio is defined by the first signal divided by the third signal, and wherein the control unit is adapted to determine the parameter of the blood as a function of a more stable one of the first and second ratios.    
     
     
         26 . A pulse oximeter, as set forth in  claim 25 , wherein the control unit is adapted to determine the parameter of the blood as a function of the more stable one of the first and second ratios and a calibration curve.  
     
     
         27 . A pulse oximeter, as set forth in  claim 26 , wherein the calibration curve is adjusted as a function of a third ratio.  
     
     
         28 . A pulse oximeter, as set forth in  claim 27 , wherein the third ratio is defined by the second signal divided by the third signal.  
     
     
         29 . A pulse oximeter, as set forth in  claim 25 , wherein the first frequency is in a red frequency range, the second frequency is in a near-infrared frequency range, and the third frequency is in an infrared frequency range.  
     
     
         30 . A pulse oximeter, as set forth in  claim 25 , wherein the control unit is adapted to track the first and second ratios and determine which one of the first and second ratios is more stable in real-time.  
     
     
         31 . A pulse oximeter for detecting a value of a parameter of blood, comprising: 
 a sensor housing;    a source of radiation coupled to the housing and being adapted to emit radiation at predetermined frequencies; and,    a plurality of detectors coupled to the housing and being adapted to detect reflected radiation at first, second, and third frequencies and to responsively generate a plurality of first sensor signals indicative of the reflected radiation at the first frequency, a plurality of second sensor signals indicative of the reflected radiation at the second frequency, and a plurality of third sensor signals indicative of the reflected radiation at the third frequency;    a control unit being coupled to the plurality of detectors and adapted to receive the plurality of first, second and third sensor signals, to analyze the first, second and third sensor signals and determine which of the first, second and third sensor signals are valid and to generate first, second, and third frequency signals as a function of valid first sensor signals, valid second sensor signals, and valid third sensor signals, respectively and to determine the parameter of the blood as a function of the valid first, second, and third sensor signals.    
     
     
         32 . A pulse oximeter, as set forth in  claim 31 , wherein the control unit is adapted to calculate first, second and third ratios of the valid first, second, and third signals and to responsively determine the parameter of the blood as a function of the first, second and third ratios.  
     
     
         33 . A pulse oximeter, as set forth in  claim 32 , wherein the control unit is adapted to determine the parameter of the blood as a function of the first and second ratios and a calibration curve.  
     
     
         34 . A pulse oximeter, as set forth in  claim 33 , wherein the calibration curve is adjusted as a function of the third ratio.  
     
     
         35 . A pulse oximeter, as set forth in  claim 32 , wherein the first ratio is defined by the valid first signals divided by the valid second signals.  
     
     
         36 . A pulse oximeter, as set forth in  claim 32 , wherein the second ratio is defined by the valid first signals divided by the valid third signals.  
     
     
         37 . A pulse oximeter, as set forth in  claim 32 , wherein the third ratio is defined by the valid second signals divided by the valid third signals.  
     
     
         38 . A pulse oximeter, as set forth in  claim 31 , wherein the first frequency is in a red frequency range, the second frequency is in a near-infrared frequency range, and the third frequency is in an infrared frequency range.  
     
     
         39 . A pulse oximeter, as set forth in  claim 32 , wherein the first ratio is defined by the valid first signals divided by the valid second signals, the second ratio is defined by the valid first signals divided by the valid third signals, and the third ratio is defined by the valid second signals divided by the valid third signals.  
     
     
         40 . A pulse oximeter, as set forth in  claim 32 , wherein the control unit is adapted to determine the parameter of the blood as a function of a more stable one of the first and second ratios.  
     
     
         41 . A pulse oximeter, as set forth in  claim 31 , wherein the plurality of first, second, and third sensor signals having an AC portion and a DC portion.  
     
     
         42 . A pulse oximeter, as set forth in  claim 41 , wherein a sensor signal is valid if it a ratio of the AC portion to the DC portion is within a predetermined range.  
     
     
         43 . A pulse oximeter, as set forth in  claim 42 , wherein the predetermined range is 0.05 to 2.0 percent.  
     
     
         44 . A sensor for use in an optical measurement device for non-invasive measurement of a blood parameter, comprising: 
 a sensor housing;    a source of radiation coupled to the housing and being adapted to emit radiation at predetermined frequencies;    a detector assembly coupled to the housing and being adapted to detect reflected radiation at least one predetermined frequency and to generate respective signals, wherein the detector assembly is ring shaped.    
     
     
         45 . A sensor, as set forth in  claim 44 , wherein the detector assembly includes a plurality of detectors arranged along a closed loop path.  
     
     
         46 . A sensor, as set forth in  claim 45 , wherein the closed loop path has a circular shape.  
     
     
         47 . A sensor, as set forth in  claim 45 , wherein the closed loop path has an elliptical shape.  
     
     
         48 . A sensor, as set forth in  claim 45 , wherein the closed loop path has a polygonal shape.  
     
     
         49 . A sensor, as set forth in  claim 44 , wherein the detector assembly includes a continuous photodetector ring.  
     
     
         50 . A sensor, as set forth in  claim 49 , wherein the continuous photodetector ring has a circular shape.  
     
     
         51 . A sensor, as set forth in  claim 49 , wherein the continuous photo detector ring has an elliptical shape.  
     
     
         52 . A sensor, as set forth in  claim 49 , wherein the continuous photo detector ring has a polygonal shape.  
     
     
         53 . A sensor, as set forth in  claim 44 , wherein the detector assembly includes a first plurality of detectors arranged along an inner closed loop path and a second plurality of detectors arranged along an outer closed loop path.  
     
     
         54 . A sensor, as set forth in  claim 53 , wherein the inner and outer closed loop paths have a circular shape.  
     
     
         55 . A sensor, as set forth in  claim 49 , wherein the inner and outer closed loop paths have an elliptical shape.  
     
     
         56 . A sensor, as set forth in  claim 49 , wherein the inner and outer closed loop paths have a polygonal shape.  
     
     
         57 . A sensor for use in an optical measurement device for non-invasive measurement of a blood parameter, comprising: 
 a sensor housing;    a source of radiation coupled to the housing and being adapted to emit radiation at predetermined frequencies;    a detector assembly coupled to the housing and being adapted to detect reflected radiation at least one predetermined frequency and to generate respective signals, wherein the detector assembly includes a plurality of pairs of detectors, each pair of detectors including a near detector and a far detector.    
     
     
         58 . A sensor, as set forth in  claim 57 , wherein the near detectors are arranged along an inner closed loop path and the far detectors are arranged along an outer closed loop paths.  
     
     
         59 . A sensor, as set forth in  claim 58 , wherein the inner and outer closed loop paths have a circular shape.  
     
     
         60 . A sensor, as set forth in  claim 58 , wherein the inner and outer closed loop paths have an elliptical shape.  
     
     
         61 . A sensor, as set forth in  claim 58 , wherein the inner and outer closed loop paths have a polygonal shape.  
     
     
         62 . A method for detecting a value of a parameter of blood using a sensor adapted to emit radiation at predetermined frequencies, to detect reflected radiation at first, second, and third frequencies and to generate respective first, second, and third signals, wherein the first, second, and third signals are indicative of a value of the reflected radiation at the respective first, second, and third frequencies, the method including the steps of: 
 receiving the first, second, and third signals;    calculating first, second and third ratios of the first, second, and third signals; and,    responsively determining the parameter of the blood as a function of the first, second and third ratios.    
     
     
         63 . A method, as set forth in  claim 62 , wherein the parameter of the blood is determined as a function of the first and second ratios and a calibration curve.  
     
     
         64 . A method, as set forth in  claim 63 , including the step of adjusting the calibration curve as a function of the third ratio.  
     
     
         65 . A method, as set forth in  claim 62 , wherein the first ratio is defined by the first signal divided by the second signal.  
     
     
         66 . A method, as set forth in  claim 62 , wherein the second ratio is defined by the first signal divided by the third signal.  
     
     
         67 . A method, as set forth in  claim 62 , wherein the third ratio is defined by the second signal divided by the third signal.  
     
     
         68 . A method, as set forth in  claim 62 , wherein the first frequency is in a red frequency range, the second frequency is in a near-infrared frequency range, and the third frequency is in an infrared frequency range.  
     
     
         69 . A method, as set forth in  claim 62 , wherein the first ratio is defined by the first signal divided by the second signal, the second ratio is defined by the first signal divided by the third signal, and the third ratio is defined by the second signal divided by the third signal.  
     
     
         70 . A method, as set forth in  claim 62 , including the step of determining a more stable of the first and second ratios, wherein the parameter of the blood is determined using the more stable one of the first and second ratios.  
     
     
         71 . A method for detecting a value of a parameter of blood using a sensor adapted to emit radiation at predetermined frequencies, to detect reflected radiation at first, second, and third frequencies and to generate respective first, second, and third signals, wherein the first, second, and third signals are indicative of a value of the reflected radiation at the respective first, second, and third frequencies, the method including the steps of: 
 receiving the first, second and third signals;    calculate first and second ratios of the first, second and third signals, wherein the first ratio is defined by the first signal divided by the second signal and the second ratio is defined by the first signal divided by the third signal; and,    determining the parameter of the blood as a function of a more stable one of the first and second ratios.    
     
     
         72 . A method, as set forth in  claim 71 , wherein the parameter of the blood as a function of the more stable one of the first and second ratios and a calibration curve.  
     
     
         73 . A method, as set forth in  claim 72 , including the step of adjusted the calibration curve as a function of a third ratio.  
     
     
         74 . A method, as set forth in  claim 73 , wherein the third ratio is defined by the second signal divided by the third signal.  
     
     
         75 . A method, as set forth in  claim 71 , wherein the first frequency is in a red frequency range, the second frequency is in an infrared frequency range, and the third frequency is in a near-infrared frequency range.  
     
     
         76 . A method, as set forth in  claim 71 , including the step of tracking the first and second ratios and determining which one of the first and second ratios is more stable in real-time.  
     
     
         77 . A method for detecting a value of a parameter of blood using a sensor adapted to emit radiation at predetermined frequencies, to detect reflected radiation at first, second, and third frequencies and to responsively generate a plurality of first sensor signals indicative of the reflected radiation at the first frequency, a plurality of second sensor signals indicative of the reflected radiation at the second frequency, and a plurality of third sensor signals indicative of the reflected radiation at the third frequency, the method comprising: 
 receiving the plurality of first, second and third sensor signals;    analyzing the first, second and third sensor signals and determining which of the first, second and third sensor signals are valid;    generating first, second, and third frequency signals as a function of valid first sensor signals, valid second sensor signals, and valid third sensor signals, respectively; and,    determining the parameter of the blood as a function of the valid first, second, and third sensor signals.    
     
     
         78 . A method, as set forth in  claim 77 , including the step of calculating first, second and third ratios of the first, second, and third valid signals and responsively determining the parameter of the blood as a function of the first, second and third ratios.  
     
     
         79 . A method, as set forth in  claim 78 , wherein the parameter of the blood is determined as a function of the first and second ratios and a calibration curve.  
     
     
         80 . A method, as set forth in  claim 79 , including the step of adjusting the calibration curve as a function of the third ratio.  
     
     
         81 . A method, as set forth in  claim 78 , wherein the first ratio is defined by the valid first signals divided by the valid second signals.  
     
     
         82 . A method, as set forth in  claim 78 , wherein the second ratio is defined by the valid first signals divided by the valid third signals.  
     
     
         83 . A method, as set forth in  claim 78 , wherein the third ratio is defined by the valid second signals divided by the valid third signals.  
     
     
         84 . A method, as set forth in  claim 78 , wherein the first frequency is in a red frequency range, the second frequency is in an infrared frequency range, and the third frequency is in a near-infrared frequency range.  
     
     
         85 . A method, as set forth in  claim 78 , wherein the first ratio is defined by the valid first signals divided by the valid second signals, the second ratio is defined by the valid first signals divided by the valid third signals, and the third ratio is defined by the valid second signals divided by the valid third signals.  
     
     
         86 . A method, as set forth in  claim 78 , including the step of determining the parameter of the blood as a function of a more stable one of the first and second ratios.  
     
     
         87 . A method, as set forth in  claim 77 , wherein the plurality of first, second, and third sensor signals have an AC portion and a DC portion.  
     
     
         88 . A method, as set forth in  claim 87 , wherein a sensor signal is valid if a ratio of the AC portion to the DC portion is within a predetermined range.  
     
     
         89 . A method, as set forth in  claim 88 , wherein the predetermined range is 0.05 to 2.0 percent.