Pulse oximeter with parallel saturation calculation modules
First Claim
1. A pulse oximeter comprising:
- a sensor configured to detect first and second electromagnetic radiation signals from a patient corresponding to first and second wavelengths of light;
an analog to digital converter, coupled to said sensor, for converting said first and second electromagnetic radiation signals into first and second digital signals; and
a processor, coupled to said analog to digital converter, said processor being programmed with a filter module for filtering said first and second digital signals, a first oxygen saturation calculation module for determining a first oxygen saturation value using a first saturation calculation algorithm applied to said first and second digital signals, a second oxygen saturation calculation module for determining a second oxygen saturation value using a second saturation calculation algorithm applied to said first and second digital signals, and an arbitration module for arbitrating by said pulse oximeter between said first and second oxygen saturation values based on a saturation confidence associated with said first and second oxygen saturation values to select a best oxygen saturation value.
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Abstract
A method and apparatus for reducing the effects of noise on a system for measuring physiological parameters, such as, for example, a pulse oximeter. The method and apparatus of the invention take into account the physical limitations on various physiological parameters being monitored when weighting and averaging a series of measurements. Varying weights are assigned different measurements, measurements are rejected, and the averaging period is adjusted according to the reliability of the measurements. Similarly, calculated values derived from analyzing the measurements are also assigned varying weights and averaged over adjustable periods. More specifically, a general class of filters such as, for example, Kalman filters, is employed in processing the measurements and calculated values. The filters use mathematical models which describe how the physiological parameters change in time, and how these parameters relate to measurement in a noisy environment. The filters adaptively modify a set of averaging weights to optimally estimate the physiological parameters.
237 Citations
34 Claims
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1. A pulse oximeter comprising:
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a sensor configured to detect first and second electromagnetic radiation signals from a patient corresponding to first and second wavelengths of light;
an analog to digital converter, coupled to said sensor, for converting said first and second electromagnetic radiation signals into first and second digital signals; and
a processor, coupled to said analog to digital converter, said processor being programmed with a filter module for filtering said first and second digital signals, a first oxygen saturation calculation module for determining a first oxygen saturation value using a first saturation calculation algorithm applied to said first and second digital signals, a second oxygen saturation calculation module for determining a second oxygen saturation value using a second saturation calculation algorithm applied to said first and second digital signals, and an arbitration module for arbitrating by said pulse oximeter between said first and second oxygen saturation values based on a saturation confidence associated with said first and second oxygen saturation values to select a best oxygen saturation value. - View Dependent Claims (2, 3, 4)
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5. A pulse oximeter comprising:
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a sensor configured to detect first and second electromagnetic radiation signals from a patient corresponding to first and second wavelengths of light;
an analog to digital converter, coupled to said sensor, for converting said first and second electromagnetic radiation signals into first and second digital signals; and
a processor, coupled to said analog to digital converter, said processor being programmed with a filter module for filtering said first and second digital signals, a normalization module for normalizing said first and second digital signals;
a first oxygen saturation calculation module for determining a first oxygen saturation value using a first saturation calculation algorithm applied to said first and second digital signals, a second oxygen saturation calculation module for determining a second oxygen saturation value using a second saturation calculation algorithm applied to said first and second digital signals, a best saturation module for arbitrating between said first and second oxygen saturation values based on a saturation confidence associated with said first and second oxygen saturation values to select a best oxygen saturation value, a first pulse rate calculation module for determining a first pulse rate from said first and second digital signals using a first pulse rate algorithm, a second pulse rate calculation module for determining a second pulse rate from said first and second digital signals using a second pulse rate algorithm, and a best rate module for arbitrating between said first and second pulse rates based on a pulse rate confidence associated with said first and second pulse rate signals to select a best pulse rate. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12)
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13. An apparatus for measuring a blood constituent, comprising:
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a plurality of blood constituent value calculators for determining a plurality of possible blood constituent values, each of the possible blood constituent values having a confidence level associated therewith based on at least one quality metric; and
an arbitrator configured to arbitrate between the plurality of possible blood constituent values with regard to the confidence levels to determine a measure of the blood constituent, said arbitrator being further configured to linearly interpolate between the plurality of possible blood constituent values to generate the measure of the blood constituent where none of the confidence levels is greater than all other confidence levels by more than a first amount.
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14. An apparatus for measuring a blood constituent using a single data set, comprising:
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a plurality of blood constituent value calculators for determining a plurality of possible blood constituent values using, each of the blood constituent value calculators using the single data set, each of the possible blood constituent values having a confidence level associated therewith based on at least one quality metric; and
an arbitrator configured to arbitrate between the plurality of possible blood constituent values with regard to the confidence levels to determine a measure of the blood constituent.
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15. An apparatus for determining a patient'"'"'s pulse rate using signals corresponding to energy transmitted through the tissue of a patient, comprising:
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a plurality of pulse rate finders for determining a plurality of possible pulse rates, each of the possible pulse rates having a confidence level associated therewith based on at least one quality metric; and
an arbitrator configured to arbitrate between the plurality of possible pulse rates with regard to the confidence levels to determine the patient'"'"'s pulse rate, including linearly interpolating between the plurality of possible pulse rates to generate the patient'"'"'s pulse rate where none of the confidence levels is greater than all other confidence levels by more than a first amount.
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16. An apparatus for determining a patient'"'"'s pulse rate using data corresponding to energy transmitted through the tissue of a patient, comprising:
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a plurality of pulse rate finders for determining a plurality of possible pulse rates, each of the possible pulse rates having a confidence level associated therewith based on at least one quality metric; and
an arbitrator configured to arbitrate between the plurality of possible pulse rates with regard to the confidence levels to determine the patient'"'"'s pulse rate, wherein one pulse rate finder includes a comb filter to remove signal energy from the data corresponding to a fundamental frequency and harmonics thereof, a frequency selector for determining a particular harmonic frequency which minimizes noise energy at an output of the comb filter, the particular harmonic frequency corresponding to the fundamental frequency, and a pulse rate generator for generating the possible pulse rate corresponding to the particular harmonic frequency. - View Dependent Claims (17, 18, 19, 20)
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21. An apparatus for determining a patient'"'"'s pulse rate using data corresponding to energy transmitted through the tissue of a patient, comprising:
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a plurality of pulse rate finders for determining a plurality of possible pulse rates, each of the possible pulse rates having a confidence level associated therewith based on at least one quality metric, wherein one pulse rate finder is configured to determine its corresponding possible pulse rate by comparing the data to a predetermined waveform template, identifying a sequence of waveform characteristics indicative of a waveform period, averaging a number of successive waveform periods to determine an average waveform period, and determining the corresponding possible pulse rate from the average waveform period; and
an arbitrator for arbitrating between the plurality of possible pulse rates with regard to the confidence levels to determine the patient'"'"'s pulse rate. - View Dependent Claims (22)
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23. An apparatus for determining a pulse rate of a patient using data corresponding to at least one wavelength of electromagnetic energy transmitted through tissue of the patient, comprising:
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an adaptive comb filter configured to track a fundamental frequency to filter the data and to thereby generate a first pulse rate, the first pulse rate having a first confidence level associated therewith based on at least one quality metric;
a comparator configured to compare the data to a predetermined waveform template to generate a second pulse rate, the second pulse rate having a second confidence level associated therewith based on the at least one quality metric; and
an arbitrator configured to arbitrate between the first and second pulse rates with regard to the first and second confidence levels to determine the patient'"'"'s pulse rate. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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Specification