Method and device for non-invasive measurements of blood parameters
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Publication Number
US-7254432-B2
Publication Date
2007-08-07
Expiration Date
Abstract
A method and system for non-invasive measurements in a patient's body in which several measurement sessions are performed on a measurement location. Each measurement session includes applying an external electromagnetic field to the measurement location, detecting at least two responses of the measurement location, and generating data indicative of the detected response. These responses are characterized by at least two different values of a controllable parameter. The measurement sessions include at least two measurement sessions carried out at a normal blood flow in the measurement location and at least two measurement sessions carried out at a condition of artificial kinetics in the measurement location. The first and second measured data are processed to determine a first relation between the first time variations and a second relation between the second time variations for the different parameter. that can be used to determine the at least one blood related parameter.
Core Innovation
The invention relates to non-invasive measurements in a patient's body by performing several measurement sessions on a measurement location on the body. Each measurement session includes illuminating the measurement location with light of at least two different wavelengths and detecting at least two light responses corresponding to the different wavelengths, thereby generating data indicative of the detected response.
The sessions include at least two measurement sessions at a first condition of normal blood flow and at least two measurement sessions at a second condition of artificial kinetics in the measurement location. For each condition, the generated time variation data are processed to determine a first relation and a second relation between time variations for the different wavelengths, each relation being determined as a parametric slope of respective time functions of the responses.
The parametric slopes are utilized to determine a certain function between the first and second relations, enabling determination of at least one blood related parameter BP using calibration coefficients and first and second parametric slopes obtained for the same pair of wavelengths. In device embodiments, a measurement unit applies an external electromagnetic field to the measurement location, a light detector arrangement detects a response of the measurement location, and a pressure applying assembly applies over-systolic pressure to create a condition of artificial kinetics characterized by blood flow cessation.
Claims Coverage
The input includes two independent claims, one method claim and one device claim, with the same core inventive structure. The claims cover multiple measurement sessions under normal blood flow and artificial kinetics conditions, processing wavelength-dependent time variations into parametric slopes, and combining relations via calibrated coefficients to determine at least one blood-related parameter.
Multiple measurement sessions under normal blood flow and artificial kinetics
Performing several measurement sessions on a measurement location on the body, each measurement session comprising illumination with light of at least two different wavelengths and detection of at least two light responses corresponding to the wavelengths; the sessions include at least two measurement sessions under normal blood flow and at least two measurement sessions under artificial kinetics.
Parametric-slope relations between time variations for different wavelengths
Processing measured data to determine a first relation between first time variations for the different wavelengths and a second relation between second time variations for the different wavelengths, each relation being determined as a parametric slope of the respective time functions of the responses.
Function between relations using calibration coefficients to determine blood-related parameter BP
Utilizing the first and second relations to determine a function between them, thereby enabling determination of at least one blood related parameter BP using calibrated coefficients and first and second parametric slopes obtained for the same pair of wavelengths.
Measurement unit with light source assembly and light detector arrangement for external electromagnetic field
A measurement unit comprising a light source assembly configured and operable for applying an external electromagnetic field to a measurement location on the body, and a light detector arrangement configured and operable for detecting a response of the measurement location to the applied field and generating data indicative thereof.
Pressure applying assembly to create artificial kinetics characterized by blood flow cessation
A pressure applying assembly configured and operable for applying over-systolic pressure to the body portion so as to create a condition of artificial kinetics in the measurement location characterized by blood flow cessation.
Control unit for sessions at parameter values under no-pressure and artificial-kinetics conditions, and for slope-based BP determination
A control unit connectable to the measurement unit and to the pressure applying assembly for operating them so as to enable several measurement sessions, receive and process response data, determine first and second measured data, determine first and second relations as parametric slopes, and utilize the relations to determine at least one blood related parameter BP.
Across the independent method and device claims, the inventive contribution is to obtain time-variation response data under normal blood flow and artificial kinetics conditions at a measurement location using illumination at at least two different wavelengths, convert those time variations into parametric-slope relations, and compute blood-related parameter(s) BP from a function that relates the normal-flow and artificial-kinetics relations using calibrated coefficients.
Stated Advantages
Improved accuracy compared with using pulse mode or occlusion mode alone, by combining pulse and occlusion signals.
Substantially increased correlation versus using either mode alone.
Documented Applications
Determination of at least one blood related parameter BP in non-invasive measurements, including hemoglobin concentration/hematocrit and oxygen saturation, and optionally other analytes such as glucose.
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