Health monitoring systems and methods
Systems, methods and devices for reducing noise in health monitoring including monitoring systems, methods and/or devices receiving a health signal and/or having at least one electrode or sensor for health monitoring.
1. A method for determining pulse transit time in an individual, the method comprising:
providing one or more ECG sensors to sense an ECG signals, and providing one or more PPG sensors to sense first and second PPG signals of first and second light wavelengths, all of the one or more ECG sensors and the one or more PPG sensors are configured to be disposed on a single health monitoring device configured to be disposed on a portion of a body;
sensing an ECG signal, the ECG signal including heartbeat information including information from one or more heartbeats; and sensing the first and second PPG signals corresponding to the first and second light wavelengths;
generating two or more PPG frames of the first and second PPG signals, the two or more PPG frames each being defined by the one or more heartbeats as included within the heartbeat information from the ECG signal and the first and second PPG signals, each of the two or more PPG frames including the first and second PPG signals occurring in an interval defined by the one or more heartbeats, the first and second PPG signals thereby being correlated with the one or more heartbeats;
creating two or more time concordance average frames from the two or more PPG frames; the two or more time-concordance average frames including a first time-concordance average frame corresponding to a first light wavelength selected from the first and second light wavelengths and a second time-concordance average frame corresponding to a second light wavelength selected from the first and second light wavelengths; the two or more time-concordance average frames being created by:
(a) measuring an ECG signal over the one or more heartbeats;
(b) measuring the first and second PPG signals over the one or more heartbeats such that the ECG signal and the first and second PPG signals are in time concordance over the one or more heartbeats;
(c) comparing a portion of the ECG signal and the first and second PPG signals in time concordance over the one or more heartbeats to determine a constant component value and a primary periodic component value of each of the first and second PPG signals; the portion of the ECG signal defining an interval within the one or more heartbeats corresponding with the PPG frames, the constant component and primary periodic component values at concordant times within intervals averaged to calculate and define the first and second time-concordance average frames, the first and second time-concordance average frames reducing signal noise; and
(d) determining oxygen saturation from constant component values and primary periodic component values of the first and second PPG signals; and,
calculating a pulse transit time from the two or more time concordance average frames, and by finding a shift in at least one of the first and second PPG signals in the one or more PPG frames with respect to the one or more heartbeats using the two or more time concordance average frames.
2. A method according to claim 1 further comprising:
calculating blood pressure from the pulse transit time.
3. A method according to claim 1 comprising generating via the ECG signal by detecting an R-wave or other ECG feature from the one or more heartbeats of an individual.
4. A method according to claim 1 comprising performing a PPG signal quality estimate.
5. A method according to claim 4 the element of performing a PPG signal quality estimate further comprising incorporating one or more of a PPG variance, an estimated PPG signal-to-noise ratio, a PPG signal saturation, a patient motion accelerometer or gyroscope data, an ECG or impedance measurement noise estimate.
6. A method according to claim 4 further comprising:
generating a gain for a frame of the two or more PPG frames from the PPG signal quality estimate in conjunction with the heartbeat information.
7. A method according to claim 6 , the generating a gain includes finding a second gain that has a lower gain value than the gain generated according to claim 6 ; the finding the second gain comprising finding a lower PPG signal quality estimate than the PPG signal quality estimate of claim 6 .
8. A method according to claim 6 the generating of a gain includes defining the PPG signal quality estimate as a constant.
9. A method according to claim 1 ,
the element of generating two or more PPG frames of PPG signal data further includes correlating the first and second PPG signals with the heartbeat information; and,
reinforcing each of the first and second PPG signals that are correlated with the heartbeat information while reducing uncorrelated noise.
10. A method according to claim 1 , the PPG signals including one or more of PPG signal samples, PPG signal noise or PPG signal response time; the method further including operating on one or more of the PPG signal samples, PPG signal noise, and PPG signal response time associated with the calculating of the pulse transit time; further including one or more of:
a number of the PPG signal samples included in the two or more PPG frames are adapted to reduce the PPG signal noise or decrease the PPG signal response time;
the two or more PPG frames are weighted; and,
the two or more PPG frames are weighted and the weighting is implemented using one or both of an IIR (infinite impulse response) or FIR (finite impulse response) filter.
11. A method according to claim 1 further comprising one or more of:
finding a sample index where the first and second PPG signals are at a minimum or a maximum and comparing it with a boundary of a PPG frame of the two or more PPG frames to determine the pulse transit time; or,
interpolating the first and second PPG signals using a spline or polynomial fit around minimum or maximum values, allowing a minimum or a maximum to be determined; or,
comparing one of the PPG frames of the two or more PPG frames to a reference frame template, shifting an average PPG frame with respect to the reference frame template; finding indication of a shift of the pulse transit time with a highest correlation between an average PPG frame and the reference frame template; further including:
the reference frame template including a predetermined signal, or
the reference frame template being adapted by using a long-term frame average with the pulse transit time.
12. A method according to claim 1 comprising performing a PPG signal quality estimate; and optionally also generating a gain for each PPG frame of the two or more PPG frames from the PPG signal quality estimate in conjunction with the heartbeat information; and,
defining the creating a time-concordance average frame including one or both of the PPG signal quality estimate and gain information with a PPG frame of the two or more PPG frames.
13. A method according to claim 1 ,
the element of generating two or more PPG frames of PPG signals further includes:
reinforcing each of the PPG signals that are with the heartbeat information while reducing uncorrelated noise.
14. A method according to claim 1 , the PPG signals including one or more of PPG signal samples, PPG signal noise or PPG signal response time; the method further including operating on one or more of the PPG signal samples, PPG signal noise, and PPG signal response time associated with the calculating off pulse transit time; further including one or more of:
a number of the PPG signal samples included in the two or more PPG frames are adapted to reduce the PPG signal noise or decrease the PPG signal response time;
the two or more PPG frames are weighted; and,
the two or more PPG frames are weighted and the weighting is implemented using one or both of an IIR (infinite impulse response) or FIR (finite impulse response) filter.
15. A method according to claim 1 further comprising one or more of:
finding a sample index where the first and second PPG signals are at a minimum or a maximum and comparing it with a boundary of a PPG frame of the two or more PPG frames to determine the pulse transit time; or,
interpolating the first and second PPG signals using a spline or polynomial fit around the minimum or the maximum values, allowing a minimum or a maximum to be determined; or,
comparing a PPG frame of the two or more PPG frames to a reference frame template, shifting an average PPG frame is shifted with respect to the reference frame template; finding indication of a shift of the pulse transit time with the highest correlation between an average PPG frame and the reference frame template; further including:
the reference frame template including a predetermined signal, or
the reference frame template being allowed to adapted by using a long-term frame average with the pulse transit time.