Device, system and method for extracting physiological information

A device for extracting physiological information indicative of at least one vital sign of a subject, said device comprising a processor configured to:

• receive from an interface at least two detection signals derived from detected electromagnetic radiation transmitted through or reflected from a skin region of a subject, wherein each detection signal comprises wavelength-dependent reflection or transmission information in a different wavelength channel,
• compute at least two signature vectors based on a reference signature vector (Pbv0),
• compute a plurality of pulse signals from said at least two detection signals using that at least two signature vectors for the computation of each pulse signal from the at least two detection signals wherein each of the at least two signature vectors is different, each of said at least two signature vectors representing expected relative pulsatilities of a corresponding one of the pulse signals, wherein the computation of each of the pulse signals involves a weighted combination of the at least two detection signals using weights resulting in pulse signals for which products with the corresponding detection signals equals the expected relative pulsatility represented by the corresponding signature vector,
• compute quality indicator values for each of the pulse signals indicating a characteristic of the corresponding one of the pulse signals,
• adapt one or more of the at least two signature vectors in a direction that depends on a one of the at least two pulse signals that yields the best quality indicator value,
• select at least one of the plurality of signature vectors based on the quality indicator values;
• derive physiological information indicative of at least one vital sign from the selected at least one of the plurality of signature vectors that results in a one of the pulse signals with the best quality indicator value or from said pulse signal, and
• transfer the physiological information to the interface for communication to a clinician,
• wherein said at least two pulse signals are computed from said at least two detection signals for said at least two signature vectors such that the one of the at least two pulse signals that correlates with said at least two detection signals in a ratio determined by a one of the signature vectors corresponding to the one of the at least two pulse signals,
• wherein computing the at least two signature vectors includes comparing said quality indicator values, increasing or decreasing a counter value depending on a sign of the comparison and using the counter value together with a predetermined update vector and the reference signature vector (Pbv0).

A method for extracting physiological information indicative of at least one vital sign of a subject, said method comprising:

• obtaining at least two detection signals derived from detected electromagnetic radiation transmitted through or reflected from a skin region of a subject, wherein each detection signal comprises wavelength-dependent reflection or transmission information in a different wavelength channel,
• computing at least two pulse signals, each of the at least two pulse signals being computed from said at least two detection signals, each of the pulse signals being computed using different ones of a plurality of signature vectors, each of the signature vectors providing an expected relative pulsatility of a corresponding one of the at least two pulse signals, wherein the computation of each of the at least two pulse signals involves a weighted combination of the at least two detection signals using weights selected such that each of the at least two pulse signals correlates with the at least two detection signals as represented by the respective signature vector,
• computing quality indicator values for each of said at least two pulse signals indicating a characteristic of each of the at least two pulse signals,
• computing a control signal CS from the quality indicator values,
• computing the plurality of signature vectors by adding update vectors (CS−1)·{right arrow over (U)} and (CS+1)·{right arrow over (U)} to a reference signature vector (Pbv0),
• adapting one or more of the plurality of signature vectors in a direction that depends on a one of the at least two pulse signals that yields the best quality indicator value,
• adapting the reference signature vector (Pbv0) based on the control signal CS to obtain the plurality of signature vectors,
• computing the at least two pulse signals from the at least two detection signals for the plurality of signature vectors such that the one of the at least two pulse signals that correlates with the at least two detection signals in a ratio determined by a one of the signature vectors corresponding to the one of the at least two pulse signals, and
• increasing the control signal CS in case the quality indicator value of the second of the at least two pulse signals is larger than a quality indicator value of a first of the at least two pulse signals and vice versa,
• deriving physiological information indicative of at least one vital sign from the signature vector that results in a one of the pulse signals with the best quality indicator value or from said one of the pulse signals with the best quality indicator value, and
• communicating the physiological information to a user.

A device for extracting physiological information indicative of at least one vital sign of a subject, said device comprising a processor configured to:

• receive from an interface at least two detection signals derived from detected electromagnetic radiation transmitted through or reflected from a skin region of a subject, wherein each detection signal comprises wavelength-dependent reflection or transmission information in a different wavelength channel,
• compute a plurality of pulse signals from said at least two detection signals using a plurality of signature vectors for the computation of each pulse signal from the at least two detection signals wherein each of the plurality of signature vectors is different, each of said signature vectors representing expected relative pulsatilities of a corresponding one of the pulse signals, wherein the computation of each of the pulse signals involves a weighted combination of the at least two detection signals using weights resulting in pulse signals for which products with the corresponding detection signals equals the expected relative pulsatility represented by the corresponding signature vector,
• compute quality indicator values for each of the pulse signals indicating a characteristic of the corresponding one of the pulse signals,
• compute a control signal CS from the quality indicator values,
• compute the plurality of signature vectors by adding update vectors (CS−1)·{right arrow over (U)} and (CS+1)·{right arrow over (U)} to a reference signature vector (Pbv0),
• adapt one or more of the plurality of signature vectors in a direction that depends on a one of the at least two pulse signals that yields the best quality indicator value,
• adapt the reference signature vector (Pbv0) based on the control signal CS to obtain the plurality of signature vectors,
• compute the plurality of pulse signals from the at least two detection signals for the plurality of signature vectors such that the one of the plurality of pulse signals that correlates with the at least two detection signals in a ratio determined by a one of the signature vectors corresponding to the one of the plurality of pulse signals, and
• increase the control signal CS in case the quality indicator value of the second of the plurality of pulse signals is larger than a quality indicator value of a first of the plurality of pulse signals and vice versa,
• select at least one of the plurality of signature vectors based on the quality indicator values;
• derive physiological information indicative of at least one vital sign from the selected at least one of the plurality of signature vectors that results in a one of the pulse signals with the best quality indicator value or from said pulse signal, and
• transfer the physiological information to the interface for communication to a clinician.