Apparatus and method for determining oxygen saturation levels with increased accuracy
First Claim
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1. Apparatus for determining the oxygen saturation level of blood under test, said apparatus comprising:
- generating and detection means for supplying radiation at three wavelengths to the blood under test and for detecting the intensity of back-scattered radiation emanating from the blood under test at each of said three wavelengths in response to the radiation so supplied, said generating and detection means including a first circuit means for generating intensity signals respectively representative of the intensity of said back-scattered radiation; and
signal processing means for computing the oxygen saturation level of the blood under test, said signal processing means including a second circuit means connected to receive said intensity signals respectively representative of the intensity of said back-scattered radiation for deriving first and second ratio signals, said signal processing means also including means connected to receive said first and second ratio signals for calculating the oxygen saturation level as a function of only said first ratio signal when said oxygen saturation level is below a predetermined value and for calculating the oxygen saturation level as a function of both said first and second ratio signals when the oxygen saturation level is above said predetermined value.
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Abstract
A catheter oximeter includes a fiber optic catheter for supplying radiation to blood under test at a plurality of wavelengths and detecting the intensities of the radiation back-scattered from the blood at each of the wavelengths. The oxygen saturation level of the blood is then computed by deriving it with a formula which uses the ratio of one pair of intensity signals when the oxygen saturation level is relatively low and with a formula which uses the ratio of another pair of intensity signals when the oxygen saturation level relatively is high.
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Citations
7 Claims
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1. Apparatus for determining the oxygen saturation level of blood under test, said apparatus comprising:
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generating and detection means for supplying radiation at three wavelengths to the blood under test and for detecting the intensity of back-scattered radiation emanating from the blood under test at each of said three wavelengths in response to the radiation so supplied, said generating and detection means including a first circuit means for generating intensity signals respectively representative of the intensity of said back-scattered radiation; and signal processing means for computing the oxygen saturation level of the blood under test, said signal processing means including a second circuit means connected to receive said intensity signals respectively representative of the intensity of said back-scattered radiation for deriving first and second ratio signals, said signal processing means also including means connected to receive said first and second ratio signals for calculating the oxygen saturation level as a function of only said first ratio signal when said oxygen saturation level is below a predetermined value and for calculating the oxygen saturation level as a function of both said first and second ratio signals when the oxygen saturation level is above said predetermined value. - View Dependent Claims (2)
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3. A method for determining the oxygen saturation level of blood under test, said method comprising the steps of:
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supplying radiation at first, second and third wavelengths to the blood under test; detecting the intensity of radiation back-scattered at each of said three wavelengths from the blood under test in response to the radiation so supplied; generating signals respectively representing the intensity of back-scattered radiation at each of said wavelengths; dividing said signals into one another to derive first and second ratios; calculating the oxygen saturation level of the blood under test as a function of only one of said ratios when the oxygen saturation level is below a predetermined value; and calculating the oxygen saturation level as a function of both of said ratios when the oxygen saturation level is above said predetermined value. - View Dependent Claims (4)
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5. Apparatus for determining the oxygen saturation level of blood under test, said apparatus comprising
means for supplying radiation at a plurality of wavelengths to the blood under test and for detecting the intensity of back-scattered radiation emanating from the blood under test at each of said wavelengths in response to the radiation so supplied, means for generating intensity signals representative of the intensity of said back-scattered radiation at each of said wavelengths, and means for computing the oxygen saturation level of the blood under test, said computing means including means connected to receive said intensity signals and generate a first ratio signal from a pair of said intensity signals and a second ratio signal from a different pair of said intensity signals, said computing means also including means connected to receive said first and second ratio signals for calculating the oxygen saturation level as a function of only said first ratio signal when said oxygen saturation level is below a predetermined value and for calculating the oxygen saturation level as a function of said second ratio signal when the oxygen saturation level is above a predetermined value.
Specification