Motion artefact rejection system for pulse oximeters
First Claim
1. In a pulse oximeter for making a measurement of blood oxygen saturation which produces pulsatile signals in response to a patient'"'"'s pulsating arterial blood flow in a first variable range of frequencies and motion artefact signals at frequencies outside of said first variable range of frequencies, apparatus for minimizing the effect of said motion artefact signals on said measurement of blood oxygen saturation comprisinga tunable bandpass filter having an input to which said pulsatile signals and said motion artefact signals are applied;
- a frequency determining means connected to the output of said tunable bandpass filter for determining the frequency of the pulsatile signals at the output of said tunable bandpass filter;
and a tuning means operatively connected to said frequency determining means and said tunable bandpass filter for tuning said tunable bandpass filter in response to said determined frequency to align the pass band of said band pass filter with the determined frequency of said pulsatile signals whereby motion artefact signals are attenuated.
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Abstract
A pulse oximeter apparatus characterized in that it comprises a bandpass filter adapted selectively to exclude motion artefact from wanted signal is disclosed.
Also disclosed is the use of such an apparatus for the determination of pulse rate and/or arterial blood oxygen saturation.
365 Citations
6 Claims
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1. In a pulse oximeter for making a measurement of blood oxygen saturation which produces pulsatile signals in response to a patient'"'"'s pulsating arterial blood flow in a first variable range of frequencies and motion artefact signals at frequencies outside of said first variable range of frequencies, apparatus for minimizing the effect of said motion artefact signals on said measurement of blood oxygen saturation comprising
a tunable bandpass filter having an input to which said pulsatile signals and said motion artefact signals are applied; -
a frequency determining means connected to the output of said tunable bandpass filter for determining the frequency of the pulsatile signals at the output of said tunable bandpass filter; and a tuning means operatively connected to said frequency determining means and said tunable bandpass filter for tuning said tunable bandpass filter in response to said determined frequency to align the pass band of said band pass filter with the determined frequency of said pulsatile signals whereby motion artefact signals are attenuated. - View Dependent Claims (2, 3, 4)
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6. In a pulse oximeter for making a measurement of blood oxygen saturation having a first channel wherein there are produced first pulsatile signals in response to red light absorbed by a patient'"'"'s pulsating arterial blood flow and a second channel wherein there are produced second pulsatile signals in response to infrared light absorbed by a patient'"'"'s pulsating arterial blood flow in a first variable range of frequencies, and in which motion artefact signals at frequencies outside of said first variable range of frequencies are produced in said first and second channels, apparatus for minimizing the effect of said motion artefact signals on said measurement of blood oxygen saturation comprising
a first tunable bandpass filter disposed in said first channel and having an input to which said first pulsatile signals and said first channel motion artefact signals are applied; -
a second tunable bandpass filter disposed in said second channel and having an input to which said second pulsatile signals and said second channel motion artefact signals are applied; a frequency determining means connected to the output of at least one of said first and second tunable bandpass filters for determining the frequency of the pulsatile signals at the output of said at least one tunable bandpass filter; and a tuning means operatively connected to said frequency determining means and said first and second tunable bandpass filters for tuning said tunable bandpass filters to align the pass bands of the band pass filters with the determined frequency. - View Dependent Claims (5)
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Specification