Monitoring device and method for estimating blood constituent concentration for tissues with low perfusion
First Claim
1. Method for estimating a hemoglobin-related blood constituent concentration of a user under low perfusion conditions:
- measuring a plurality of photoplethysmographic (PPG) signals by using a spectrophotometry-based monitoring device comprising a multichannel sensor formed from a plurality of channels, each PPG signal being measured by one of the channels;
measuring a cardio-synchronous (CV) signal by using a cardiovascular sensor of the spectrophotometry-based monitoring device; and
using a signal processor configured for;
detecting an instantaneous heart rate and determining a heart rate variability from the CV signal;
for each detected heart rate, determining projected PPG signals by projecting the measured PPG signals multiplied by a window function on a principal frequency component, and determining a magnitude of the projected PPG signals as the sum of the projected PPG signals;
selecting reliable projected PPG signals, wherein reliable projected PPG signals are projected PPG signals which have a predetermined magnitude and a predetermined phase and/or coherence between the PPG signals and the principal frequency component;
estimating a value of said blood constituent concentration from the magnitude of said reliable projected PPG signals selected over a predetermined time period;
said window function having a window length which is adjusted at each detected heart rate according to the determined heart rate variability; and
the frequency of said principal frequency component being estimated by averaging the heart rate over the window length.
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Accused Products
Abstract
The present disclosure relates to a method for estimating blood constituent concentration of a user under low perfusion conditions using a spectrophotometry-based monitoring device; the method comprising: measuring a plurality of photoplethysmographic (PPG) signals; measuring a cardio-synchronous (CV) signal; detecting an instantaneous heart rate and determining a heart rate variability from the CV signal; selecting reliable projected PPG signals; estimating a value of said blood constituent concentration from the magnitude of said reliable projected PPG signals. The disclosed method requires diminished computational load compared to conventional methods based on frequency domain approach as FFT or DCT. The disclosure also pertains to a monitoring device for estimating blood constituent concentration in tissue under low perfusion of a user.
11 Citations
22 Claims
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1. Method for estimating a hemoglobin-related blood constituent concentration of a user under low perfusion conditions:
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measuring a plurality of photoplethysmographic (PPG) signals by using a spectrophotometry-based monitoring device comprising a multichannel sensor formed from a plurality of channels, each PPG signal being measured by one of the channels; measuring a cardio-synchronous (CV) signal by using a cardiovascular sensor of the spectrophotometry-based monitoring device; and using a signal processor configured for; detecting an instantaneous heart rate and determining a heart rate variability from the CV signal; for each detected heart rate, determining projected PPG signals by projecting the measured PPG signals multiplied by a window function on a principal frequency component, and determining a magnitude of the projected PPG signals as the sum of the projected PPG signals; selecting reliable projected PPG signals, wherein reliable projected PPG signals are projected PPG signals which have a predetermined magnitude and a predetermined phase and/or coherence between the PPG signals and the principal frequency component; estimating a value of said blood constituent concentration from the magnitude of said reliable projected PPG signals selected over a predetermined time period; said window function having a window length which is adjusted at each detected heart rate according to the determined heart rate variability; and the frequency of said principal frequency component being estimated by averaging the heart rate over the window length. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. Monitoring device for estimating a hemoglobin-related blood constituent concentration in tissue under low perfusion of a user comprising:
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a multichannel sensor formed from a plurality of photoplethysmographic (PPG) sensor channels, each PPG sensor channel configured to measure a PPG signal; a cardiovascular sensor configured to measure a cardio-synchronous (CV) signal; and a signal processor configured to; detect an instantaneous heart rate and determine a heart rate variability from the CV signal; for each detected heart rate, determining projected PPG signals by projecting the measured PPG signals multiplied by a window function on a principal frequency component, and determining a magnitude of the projected PPG signals as the sum of the projected PPG signals; select reliable projected PPG signals, wherein reliable projected PPG signals are projected PPG signals which have a predetermined magnitude and a predetermined phase and/or coherence between the PPG signals and the principal frequency component; estimate a value of said blood constituent concentration from the magnitude of said reliable projected PPG signals selected over a predetermined time period; said window function having a window length which is adjusted at each detected heart rate according to the determined heart rate variability; and the frequency of said principal frequency component being estimated by averaging the heart rate over the window length. - View Dependent Claims (16, 17, 18, 19, 20)
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21. Method for estimating a hemoglobin-related blood constituent concentration of a user under low perfusion conditions, comprising:
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measuring a plurality of photoplethysmographic (PPG) signals by using a spectrophotometry-based monitoring device comprising a multichannel sensor formed from a plurality of channels, each PPG signal being measured by one of the channels; measuring a cardio-synchronous (CV) signal by using a cardiovascular sensor of the spectrophotometry-based monitoring device; and using a signal processor configured for; detecting an instantaneous heart rate and determining a heart rate variability from the CV signal; for each detected heart rate, determining projected PPG signals by projecting the measured PPG signals multiplied by a window function on a principal frequency component, and determining a magnitude of the projected PPG signals as the sum of the projected measured PPG signals; selecting reliable projected PPG signals, wherein reliable projected PPG signals are projected PPG signals which have a magnitude at least twice the noise floor, or a coherence between the PPG signals and the principal frequency component having a value equal or above 0.7, or the phase being less than a maximal angle resulting in a linear phase relationship between the phase and a maximally elapsed time between the occurrence of the heart beat and PPG pulse wave at the sensor location; estimating a value of said blood constituent concentration from the magnitude of said reliable projected PPG signals selected over a predetermined time period; said window function having a window length which is adjusted at each detected heart rate according to the determined heart rate variability; and the frequency of said principal frequency component being estimated by averaging the heart rate over the window length. - View Dependent Claims (22)
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Specification