Method and apparatus for calculating arterial oxygen saturation based plethysmographs including transients
DC CAFCFirst Claim
1. Apparatus for compensating distortion in transmittance caused by transient conditions in a patient'"'"'s plethysmograph waveform having periodic changes related to the patient'"'"'s beating heart, aperiodic changes unrelated to the beating heart, background transmittance, and transient background transmittance changes at frequencies below the heart rate for use in an oximeter device, comprising:
- means for receiving a detected optical signal corresponding to the transmittance of a first and second light frequency passing through the patient'"'"'s tissue;
filter means for eliminating frequency components of the detected optical signal other than those that have a frequency below the frequency of the fundamental heart rate, thereby providing a filtered signal; and
dividing means for dividing the detected optical signal by the filtered signal in phase, thereby providing a compensated optical signal.
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Abstract
A method and apparatus for improving the calculation of oxygen saturation by non-invasive pulse oximeters during transient conditions. Transient conditions introduce artifactual errors into the detected optical signal because of changes in transmittance of the light with localized blood volume changes and as the average background oxygen saturation level of the patient'"'"'s blood changes. The invention relates to correcting the detected optical pulses by linear interpolation and rate of change techniques or by selective frequency filtering and compensating the detected optical signal using the filtered signal to provide accurate estimates of oxygen saturation during transient conditions.
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Citations
14 Claims
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1. Apparatus for compensating distortion in transmittance caused by transient conditions in a patient'"'"'s plethysmograph waveform having periodic changes related to the patient'"'"'s beating heart, aperiodic changes unrelated to the beating heart, background transmittance, and transient background transmittance changes at frequencies below the heart rate for use in an oximeter device, comprising:
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means for receiving a detected optical signal corresponding to the transmittance of a first and second light frequency passing through the patient'"'"'s tissue; filter means for eliminating frequency components of the detected optical signal other than those that have a frequency below the frequency of the fundamental heart rate, thereby providing a filtered signal; and dividing means for dividing the detected optical signal by the filtered signal in phase, thereby providing a compensated optical signal. - View Dependent Claims (2, 3, 4, 5)
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6. Apparatus for compensating distortion in transmittance caused by transient conditions in a patient'"'"'s plethysmograph waveform having periodic changes related to the patient'"'"'s beating heart, aperiodic changes unrelated to the beating heart, background transmittance, and transient background transmittance changes at frequencies below the heart rate for use in an oximeter device, comprising:
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means for receiving first and second optical signals corresponding to the transmittance of first and second light frequencies passing through the patient'"'"'s tissue; first filter means for eliminating the frequency components of the first optical signal other than those that are below the fundamental heart rate, thereby providing a first filtered signal; second filter means for eliminating the frequency components of the second optical signal other than those that are below the fundamental heart rate, thereby providing a second filtered signal; a first dividing means for dividing the first optical signal by the first filtered signal in phase, thereby providing a compensated first optical signal; and a second dividing means for dividing the second optical signal by the second filtered signal in phase, thereby providing a compensated second optical signal. - View Dependent Claims (7, 8, 9, 10)
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11. A method for detecting and processing arterial pulses of a patient during transient conditions comprising:
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passing a first light frequency through the patient'"'"'s tissue and detecting a first optical signal corresponding to changes in the transmittance of the first frequency including periodic transmittance changes related to the patient'"'"'s beating heart, aperiodic transmittance changes unrelated to the beating heart, background transmittance, and transient background transmittance changes at frequencies below the heart rate; passing a second light frequency through the patient'"'"'s tissue and detecting a second optical signal corresponding to changes in the transmittance of a second frequency including periodic transmittance changes related to the patient'"'"'s beating heart, aperiodic transmittance changes unrelated to the beating heart, background transmittance, and transient background transmittance changes at frequencies below the heart rate; and
, for each of the first and second detected optical signals;processing the first and second detected optical signals to obtain first and second filtered signals substantially comprising the background transmittance and transient background transmittance components of the first and second detected optical signals below the heart rate frequency; and adjusting the first and second detected optical signals by dividing the first and second detected optical signals by the first and second filtered signals, respectively, in phase, thereby providing compensated first and second optical signals. - View Dependent Claims (12, 13, 14)
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Specification