Pulse amplitude indexing method and apparatus
First Claim
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1. A device for the monitoring of a physiological characteristic of a patient'"'"'s blood, comprising:
- a first radiation emitter that emits light at a first wavelength;
a second radiation emitter that emits light at a second wavelength;
a radiation detector configured to receive light at said first and second wavelengths after absorbance through said patient'"'"'s blood and provide a first intensity signal and a second intensity signal corresponding to said first and second received wavelengths; and
a controller for computing said physiological characteristic of said patient'"'"'s blood by determining a pulse amplitude associated with said first and second intensity signals and indexing a monitored mathematical combination of said first and second intensity signals to said determined pulse amplitude, wherein said monitored mathematical combination is related to said physiological characteristic and calculated from said first and second intensity signals.
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Abstract
The invention is method and apparatus for determining a physiological characteristic by detecting the intensity of light following tissue absorption at two wavelengths, estimating the pulse amplitude and indexing a calculated physiological characteristic to the estimated pulse amplitude. In one embodiment, the ratio of logarithms of absorbance signal amplitude is indexed to the pulse amplitude to improve the accuracy of arterial oxygen saturation as determined by a pulse oximeter.
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28 Claims
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1. A device for the monitoring of a physiological characteristic of a patient'"'"'s blood, comprising:
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a first radiation emitter that emits light at a first wavelength; a second radiation emitter that emits light at a second wavelength; a radiation detector configured to receive light at said first and second wavelengths after absorbance through said patient'"'"'s blood and provide a first intensity signal and a second intensity signal corresponding to said first and second received wavelengths; and a controller for computing said physiological characteristic of said patient'"'"'s blood by determining a pulse amplitude associated with said first and second intensity signals and indexing a monitored mathematical combination of said first and second intensity signals to said determined pulse amplitude, wherein said monitored mathematical combination is related to said physiological characteristic and calculated from said first and second intensity signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for processing signals reflecting a physiological characteristic of a patient'"'"'s blood, comprising the steps of:
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coupling an oximeter sensor arrangement to a tissue region of said patient; passing first and second lights through said patient'"'"'s tissue region, wherein said first light is substantially in a red light range and said second light is substantially in an infrared light range; determining a pulse amplitude associated with said first and second intensity signals; calculating a monitored mathematical combination from said first and second intensity signals, wherein said monitored mathematical combination is related to said physiological characteristic; and indexing said monitored mathematical combination to said determined pulse amplitude. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. A method for determining a subject'"'"'s arterial oxygen saturation comprising the steps of:
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determining arterial oxygen saturation as a function of a mathematical combination of two optical signals at each of a plurality of specific pulse amplitudes; storing said arterial oxygen saturation functions; obtaining oximetry data from a subject; determining said subject'"'"'s pulse amplitude; monitoring a mathematical combination of two optical signals obtained from said oximetry data; selecting a stored arterial oxygen saturation function having the closest pulse amplitude to said determined pulse amplitude; and determining said subject'"'"'s arterial oxygen saturation from said monitored mathematical combination and said stored arterial oxygen saturation function having the closest pulse amplitude. - View Dependent Claims (28)
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Specification