Patent ID: 11896405
Assignee: HEMOCEPT INC.
Field: nan (nan)
Classification: CPC nan | IPC A  G

Claim 13:
14. A system for determining venous oxygen saturation, comprising:
(a) a device positionable against skin of a person;
(b) at least one PPG sensor mounted on the device for measuring a PPG signal of the person at multiple wavelengths of light;
(c) a plurality of electrodes for measuring an EKG signal of the person;
(d) a computer logic system for receiving and analyzing the PPG signal and the EKG signal,
wherein the computer logic system is configured to:
identify cardiac cycles in the EKG signal;
segment the PPG signal into a series of PPG signal segments based upon features in the identified cardiac cycles,
sort the PPG signal segments into a plurality of bins based upon a similarity in durations of prior R-to-R cardiac cycles and a similarity in durations of current R-to-R cardiac cycles,
generate a composite signal for each of the plurality of bins by summing or averaging the PPG signal segments in the bin, and
generate composite Signal Prime Over Signal (SPOS) for each of the composite signals by calculating a derivative of the composite signal and normalizing the derivative of the composite signal by the composite signal itself, and
measure venous oxygen saturation of the person by:
(a) calculating arterial oxygen saturation by comparing the composite SPOS signals measured at different wavelengths of light,
(b) sub-sampling composite signals at two consecutive signal maxima measured at different wavelengths of light, and
(c) comparing the sub-sampled composite signals measured at different wavelengths of light to the calculated arterial oxygen saturation to determine venous oxygen saturation.