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

Claim 0:
1. 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 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,
generate a 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,
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 SPOS signals measured at different wavelengths of light to the calculated arterial oxygen saturation to determine venous oxygen saturation, and
output to a display device an indication of the determined venous oxygen saturation to enable noninvasive monitoring of cardiac conditions.