Spacelabs Medical, Inc.

Jonathan Tien

David R Marble

A technique for the algebraic derivation of a pulse oximetry signal uses the mathematical relations of detected light signals. First and second light sources transmit light through the patient's finger or reflects light off the blood vessels in the patient's finger. A light detector detects light from each of the light sources and generates a measured intensity signal. The measured intensity signal includes the true intensity of light transmitted from each of the light sources as well as noise introduced during the measurement process. A data sample from each of the light sources is digitized and subdivided into a plurality of data windows. The mathematical relationship is applied to each of the data windows to determine a ratio value indicative of oxygen saturation in the patient. The ratio values are statistically analyzed to determine the best estimate for the correct ratio value. This ratio value is subsequently processed to determine the oxygen saturation within the patient.

System and method for the algebraic derivation of physiological signals

A technique for the accurate determination of artifact free pulse oximetry signals utilizes an adaptive signal processor and peak detector circuit. A reference signal for the adaptive signal processor is derived based on mathematical relations of the detected light signals and the true intensity of light signals. The derivation of the appropriate reference signal requires the determination of peak values for two ratio constants. The two ratio constants lie within a known physiological range of values. When the value of the ratio constants has been determined, the reference signal equals the true intensity. The output of the adaptive signal processor is provided to the peak detector. The peak detector subdivides the known physiological range into two intervals and determines in which interval a peak exists. The remaining interval is discarded, and the peak detector repeats the measurement on the remaining interval until a peak has been detected within the desired accuracy. The value corresponding to the detected peak is one of the ratio constants. In a second alternative embodiment, the output of the adaptive filter is fed directly to the peak detector to determine values for the two ratio constants. In yet a third embodiment, two adaptive signal processors are coupled to a ratio processor. The output of the ratio processor is at a minimum when the appropriate value is selected for each of the two ratio constants.

System and method for the extractment of physiological signals

A technique for the derivation of a pulse oximetry signal using fractal dimension analysis of detected light signals. First and second light sources transmit light through the patient's finger or reflect light off the blood vessels in the patient's finger. A light detector detects light from each of the light sources and generates a measured intensity signal. The measured intensity signal includes the true intensity of light transmitted from each of the light sources as well as noise introduced during the measurement process. A data sample from each of the light sources is digitized and a set of equations developed as a function of a ratio value indicative of oxygen saturation in the patient. The fractal dimension is determined for the set of signal functions over the normal physiological range for the ratio value. Maximum and/or minimum fractal dimension values are calculated to determine the desired ratio values which are possible indicatives of the ratio of true physiological signals or noise signals. The ratio values are subsequently processed to determine the oxygen saturation within the patient.

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Redmond, WA, United States of America

Jonathan Tien