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  Adjusting parameters used in pulse oximetry analysisUSPTO Application #: 20070100220Title: Adjusting parameters used in pulse oximetry analysis Abstract: Adjusting a pulse qualification criterion includes receiving a signal representing a plurality of pulses, where the signal is generated in response to detecting light scattered from blood perfused tissue. A characteristic is determined. A pulse qualification criterion used for qualifying a pulse is adjusted in accordance with the characteristic. The pulses are evaluated according to the pulse qualification criterion. (end of abstract)
Agent: Fletcher Yoder (tyco International, Ltd.) - Houston, TX, US Inventor: Clark R. Baker USPTO Applicaton #: 20070100220 - Class: 600323000 (USPTO) Related Patent Categories: Surgery, Diagnostic Testing, Measuring Or Detecting Nonradioactive Constituent Of Body Liquid By Means Placed Against Or In Body Throughout Test, Infrared, Visible Light, Or Ultraviolet Radiation Directed On Or Through Body Or Constituent Released Therefrom, Determining Blood Constituent, Oxygen Saturation, E.g., Oximeter The Patent Description & Claims data below is from USPTO Patent Application 20070100220. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] This invention relates generally to the field of medical devices and, more particularly, to adjusting parameters used in pulse oximetry analysis. BACKGROUND [0002] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. [0003] A pulse oximeter is a medical device that may be used to measure various blood characteristics, for example, the oxygen saturation of hemoglobin in pulsing blood and/or the pulse rate of a patient. To measure these characteristics, a non-invasive sensor may be used to pass light through a portion of blood perfused tissue and photo-electrically sense the absorption and scattering of light in the tissue. The amount of light absorbed and/or scattered is analyzed to estimate the amount of blood constituent in the tissue. [0004] A detector signal resulting from measurement of the light describes the blood characteristics. As an example, pulses refer to the varying amount of arterial blood present in the tissue during a cardiac cycle. The varying amount of arterial blood yields cyclic attenuation of the light passing through the tissue. Accordingly, the detector signal from measurement of the light exhibits the familiar plethysmographic waveform. [0005] Analysis of detector signals involves processes that use various parameters. As an example, the analysis may involve filtering estimates of hemoglobin saturation to improve the accuracy of the saturation estimates. As another example, the analysis may involve filtering of plethysmographic waveforms. The filtering may use parameters such as filter weights or coefficients to adjust the filtering process. As another example, the analysis may involve applying pulse qualification criteria to qualify or disqualify pulses. The pulse qualification criteria may include parameters used to adjust the pulse qualification. [0006] It is desirable to provide a flexible and robust methodology for adjusting the parameters of oximetry analysis. SUMMARY [0007] Certain aspects commensurate in scope with the originally claimed invention are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below. [0008] In accordance with one aspect of the present invention, there is provided a method for adjusting a pulse qualification criterion. The method may include receiving a signal representing a plurality of pulses, where the signal is generated in response to detecting light scattered from blood perfused tissue. A filter parameter value of a filter parameter of a filter may be determined, where the filter may be operable to filter the signal. A pulse qualification criterion may be adjusted in accordance with the filter parameter value, where the pulse qualification criterion may be used for qualifying a pulse. The pulses may be evaluated according to the pulse qualification criterion. [0009] In accordance with another aspect of the present invention, there is provided a method for adjusting a pulse qualification criterion. The method may include receiving a signal representing a plurality of pulses, where the signal may be generated in response to detecting light scattered from blood perfused tissue. Each pulse may have an amplitude and a period, and a subset of the pulses may have a plurality of amplitudes and a plurality of periods. An average amplitude may be determined from the plurality of amplitudes, and an average period may be determined from the plurality of periods. A pulse qualification criterion may be adjusted in accordance with the average amplitude and the average period. Pulses may be evaluated according to the pulse qualification criterion. [0010] In accordance with another aspect of the present invention, there is provided a method for adjusting a filter weight of a saturation filtering process. The method may include receiving a signal representing a plurality of pulses, where the signal may be generated in response to detecting light scattered from blood perfused tissue. The light may comprise a red waveform and an infrared waveform. A ratio-of-ratios variability metric indicating the variation of a ratio-of-ratios may be determined. A ratio-of-ratios may represent the ratio of absorbances of the red waveform and the infrared waveform. A pulse quality metric indicating the quality of one or more pulses may be determined. A saturation filter weight may be adjusted in accordance with the ratio-of-ratios variability metric and the pulse quality metric, where the saturation filter weight may represent a weight used for a filtering process operable to filter a saturation estimate of the blood perfused tissue. BRIEF DESCRIPTION OF THE DRAWINGS [0011] Certain exemplary embodiments are described in the following detailed description and in reference to the drawings in which: [0012] FIG. 1 is a block diagram of one embodiment of a pulse oximeter that may be configured to implement embodiments of the present invention; [0013] FIG. 2 is a block diagram of a signal processing system of a pulse oximeter in accordance with one embodiment of the present invention; [0014] FIG. 3 is a flowchart illustrating one embodiment of a method for adjusting a noise gate parameter of a noise gate criterion in accordance with an ensemble averaging weight; [0015] FIG. 4 is a flowchart illustrating one embodiment of a method for adjusting a pulse period criterion in accordance with an ensemble averaging weight; [0016] FIG. 5 is a flowchart illustrating one embodiment of a method for adjusting a pulse amplitude criterion in accordance with an average pulse amplitude and an average pulse period; [0017] FIG. 6 is a flowchart illustrating one embodiment of a method for adjusting a saturation weight in accordance with a pulse quality metric; and [0018] FIG. 7 is a flowchart illustrating an embodiment of a method for adjusting a saturation weight in accordance with a ratio-of-ratios variability metric and a pulse quality metric. DETAILED DESCRIPTION [0019] The exemplary embodiments described below are best understood by referring to FIGS. 1 through 6 of the drawings, like numerals being used for like and corresponding parts of the various drawings. The methods and systems in accordance with these exemplary embodiments are directed towards adjusting parameters of oximetry analysis. These embodiments may be particularly applicable to and thus, are explained by reference to measuring oxygen saturation and qualifying pulses, as applicable to pulse oximeter monitors and pulse oximetry sensors. It should be realized, however, that the embodiments may be applicable to any generalized patient monitor and associated patient sensor, such as, for example, an electrocardiograph (ECG), blood pressure monitor, etc., and are thus, also applicable to nonoximetry methods and systems. Continue reading... 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