Apparatus and method for enhancing and analyzing signals from a continuous non-invasive blood pressure device
Inventors
Fortin, Jürgen • GRÜLLENBERGER, RUPERT
Assignees
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Publication Number
US-8814800-B2
Publication Date
2014-08-26
Expiration Date
Abstract
A system and method of enhancing a blood pressure signal is disclosed. The volume of an artery in a finger is measured by a photo-plesthysmographic (PPG) system, which produces a PPG signal. This PPG system is placed inside a cuff, and the cuff pressure is controlled by the PPG signal. The portion or component of the PPG signal having a frequency higher than a predefined threshold frequency is then modified or enhanced, such as by multiplying the high frequency component by a calibration factor. A blood pressure signal is then calculated using the cuff pressure and the modified PPG signal. A blood pressure contour curve may then be generated, and a variety of parameters may be calculated using the curve.
Core Innovation
The invention relates to a method for determining a blood pressure contour curve using a finger cuff having a photo-plethysmographic (PPG) system. The PPG system produces a PPG signal based on volume of the artery in a human finger, where the PPG system includes at least one light source and at least one light detector. A computing device modifies the PPG signal and derives a blood pressure signal from the modified PPG signal used for calculating the blood pressure contour curve.
A key aspect is modifying a component of the PPG signal having a frequency higher than a predefined threshold frequency by eliminating an undesired portion of the PPG signal and reconstructing the PPG signal from the remaining portion. In this framework, the cuff pressure is controlled by the modified PPG signal component, and the computing device calculates a blood pressure signal using at least the modified component. The disclosed modifications target undesired frequency bands related to vasomotor activity.
The invention further enables fidelity enhancement of the derived blood pressure signal by modifying only PPG/pressure components above a predefined frequency threshold and reconstructing or eliminating undesired frequency bands, including very-low-frequency components related to vasomotor activity. The disclosed approach includes calibration to an upper-arm NBP and multi-frequency control loops, and it supports generating a blood pressure contour curve for parameter calculation.
Claims Coverage
The document includes two independent claims that cover both a method and a device for determining a blood pressure contour curve. Across the independent claims, four main inventive elements are consistently emphasized.
Finger cuff PPG placement and PPG signal generation
A cuff adapted to be placed over an artery in a human finger, where the cuff includes a PPG system producing a PPG signal based on volume of the artery, the PPG system including at least one light source and at least one light detector.
Frequency-threshold modification of the PPG signal via elimination and reconstruction
Modifying, by a computing device, a component of the PPG signal having a frequency higher than a predefined threshold frequency by eliminating from the PPG signal an undesired portion of the PPG signal and reconstructing the PPG signal from the remaining portion of the PPG signal.
Cuff pressure control using one or more modified PPG components
The cuff pressure being controlled by one or more components of the modified PPG signal; and a controller for controlling the pressure in the cuff, wherein the controller uses the one or more components of the modified PPG signal to control the pressure in the cuff.
Blood pressure signal calculation from modified PPG components to determine a contour curve
Calculating, by the computing device, a blood pressure signal using at least the modified component of the PPG signal; and calculating a blood pressure signal by the computing device using the cuff pressure and the modified PPG signal for determining the blood pressure contour curve.
The independent claims jointly require a finger cuff with a PPG system and pressure sensing, modification of a PPG component above a predefined threshold by eliminating an undesired portion and reconstructing the PPG signal, and computation of a blood pressure signal from the modified component and cuff pressure to determine a blood pressure contour curve.
Stated Advantages
Enhances the fidelity of the derived blood pressure signal by modifying only PPG/pressure components above a predefined frequency threshold.
Enables generation of a blood pressure contour curve for calculating physiological parameters such as SV, CO, PPV, TPR, and arterial stiffness.
Supports interfacing with other monitors/IBP inputs through potential height (hydrostatic) correction and scaling.
Documented Applications
Calculating parameters from a blood pressure contour curve, including stroke volume (SV), cardiac output (CO), stroke volume variation (SVV), pulse pressure variation (PPV), total peripheral resistance (TPR), and arterial stiffness.
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