System and method for health monitoring using a non-invasive, multi-band biosensor
A biosensor includes a PPG circuit that emits light directed at living tissue at a plurality of wavelengths. A first and second spectral response of light reflected from the tissue is obtained around a first wavelength and a second wavelength. Using absorption coefficients for substances at the plurality of wavelengths, concentration levels of a plurality of substances may then be determined from the spectral responses. This embodiment of the biosensor may thus be used to determine concentrations of a plurality of substances in arterial blood flow using the spectral response.
1. A biosensor, comprising:
a PPG circuit configured to:
emit light having at least a first wavelength responsive to nitric oxide (NO) levels directed at an outer epidermal layer of skin tissue of a patient;
emit light having at least a second wavelength with a low absorption coefficient for nitric oxide (NO) directed at the outer epidermal layer of skin tissue of the patient;
generate a first spectral response for light detected around the first wavelength responsive to NO levels from the outer epidermal layer of the skin tissue of the patient;
generate a second spectral response for light detected around the second wavelength with a low absorption coefficient for NO from the outer epidermal layer of the skin tissue of the patient;
a processing circuit configured to obtain an indicator of a concentration level of NO of the patient, wherein the processing circuit is configured to:
isolate a systolic point and a diastolic point in the first spectral response and obtain a value L λ1 using a ratio of the systolic point and the diastolic point in the first spectral response;
isolate a systolic point and a diastolic point in the second spectral response and obtain a value L λ2 using a ratio of the systolic point and diastolic point in the second spectral response;
obtain a value R λ1,λ2 from a ratio of the value L λ1 and the value L λ2 , wherein the value R λ1,λ2 is the indicator of the concentration level of NO of the patient;
obtain a blood glucose concentration level of the patient from a calibration table using the value R λ1,λ2 , wherein the calibration table includes a range of R λ1,λ2 values and correlated blood glucose concentration levels; and
transmit the blood glucose concentration level of the patient for display.
2. The biosensor of claim 1 , wherein the first spectral response generated for light detected around the first wavelength responsive to NO levels is responsive to the NO levels generated during an insulin response after caloric intake in pulsating arterial blood flow.
3. The biosensor of claim 1 , wherein the indicator of the concentration level of NO of the patient value R λ1,λ2 is responsive to a base insulin resistance factor measured after a period of fasting and correlates to an indicator of diabetic risk of the patient.
4. The biosensor of claim 3 , wherein the processing circuit is further configured to determine the indicator of the diabetic risk of the patient using the base insulin resistance factor.
5. The biosensor of claim 4 , wherein the processing circuit is further configured to output an indicator of no diabetic risk in response to determining a base insulin resistance factor that correlates to average NO levels of a sample population.
6. The biosensor of claim 5 , wherein the processing circuit is further configured to output an indicator of a diabetic condition in response to determining a base insulin resistance factor that correlates to NO levels of at least less than 25% of average NO levels of a sample population.
7. The biosensor of claim 6 , wherein the first frequency is approximately 390 nm.
8. The biosensor of claim 5 , wherein the PPG circuit is configured to generate the first spectral response for light detected at the wavelength of 390 nm and for wavelengths in a range of 1 nm to 50 nm around 390 nm.
9. The biosensor of claim 8 , wherein the calibration table is generated using blood glucose level measurements obtained from a sample population during a same measurement period as the range of R λ1,λ2 values is obtained by the biosensor for the sample population.
10. A biosensor, comprising:
a PPG circuit configured to:
generate at least a first spectral response for light reflected around a first wavelength from skin tissue of the patient, wherein the first wavelength is responsive to nitric oxide (NO) levels in arterial blood flow;
generate at least a second spectral response for light detected around a second wavelength reflected from the skin tissue of the patient, wherein the second wavelength has a low absorption coefficient for nitric oxide (NO) in arterial blood flow;
a processing circuit configured to obtain a glucose concentration level of the patient, wherein the processing circuit is configured to:
obtain a value L λ1 using the first spectral response, wherein the value L λ1 isolates the first spectral response due to pulsating arterial blood flow;
obtain a value L λ2 using the second spectral response, wherein the value L λ2 isolates the second spectral response due to pulsating arterial blood flow;
obtain a value R λ1,λ2 from a ratio of the value L λ1 and the value L λ2 , wherein the value R λ1,λ2 indicates a concentration level of NO of the patient;
obtain a base insulin resistance factor based on the value R λ1,λ2 that indicates a diabetic risk indicator;
a wireless transceiver configured to transmit the diabetic risk indicator to a remote device.
11. The biosensor of claim 10 , wherein the processing circuit is further configured to output an indicator of no diabetic risk based on an obtained R value in at least an upper 60% range of R values.
12. The biosensor of claim 11 , wherein the processing circuit is further configured to output an indicator of a diabetic condition based on an obtained R value in at least a lower 10% range of R values.
13. The biosensor of claim 12 , wherein the first spectral response generated for light detected around the first wavelength is responsive to NO levels from an insulin response after caloric intake in pulsating arterial blood flow.
14. The biosensor of claim 13 , wherein the first frequency is approximately 390 nm.
15. The biosensor of claim 14 , wherein the PPG circuit is configured to generate the first spectral response for light detected at the wavelength of 390 nm and for wavelengths in a range of 1 nm to 50 nm around 390 nm.
16. The biosensor of claim 10 , wherein the processing circuit is further configured to obtain a blood glucose concentration level detected from an insulin response using a calibration table and the value R λ1,λ2 .
17. The biosensor of claim 16 , wherein the calibration table includes a range of R λ1,λ2 values and correlated blood glucose levels, wherein the calibration table is generated using blood glucose level measurements obtained from a sample population during a same measurement period as the range of R λ1,λ2 values is obtained by the biosensor of the sample population.
18. The biosensor of claim 10 , wherein the PPG circuit is further configured to:
generate at least a third spectral response for light reflected around a third wavelength from skin tissue of the patient, wherein the third wavelength is responsive to an additional substance including at least one of: a blood alcohol level, a liver enzyme level, a cancer indicating protein, a sodium chloride level, a potassium level, an iron level and a white blood cell level; and
generate at least a fourth spectral response for light reflected around a fourth wavelength from skin tissue of the patient, wherein the fourth wavelength has a low absorbance coefficient for the additional substance.
19. The biosensor of claim 18 , wherein the processing circuit further configured to:
obtain a value L λ3 using the third spectral response, wherein the value L λ3 isolates the third spectral response due to pulsating arterial blood flow;
obtain a concentration level of the additional substance using a linear function from at least the L λ3 , L λ4 values and absorption coefficients of the substance at the third wavelength and the fourth wavelength.
20. A method for health monitoring, comprising:
generating at least a first spectral response for light reflected around a first wavelength from skin tissue of the patient, wherein the first wavelength is responsive to nitric oxide (NO) levels in arterial blood flow;
generating at least a second spectral response for light detected around a second wavelength reflected from the skin tissue of the patient, wherein the second wavelength has a low absorption coefficient for nitric oxide (NO) in arterial blood flow;
obtaining a value L λ1 using the first spectral response, wherein the value L λ1 isolates the first spectral response due to pulsating arterial blood flow;
obtaining a value L λ2 using the second spectral response, wherein the value L λ2 isolates the second spectral response due to pulsating arterial blood flow;
obtaining a value R λ1,λ2 from a ratio of the value L λ1 and the value L λ2 , wherein the value R λ1,λ2 indicates a concentration level of NO of the patient;
obtaining a base insulin resistance factor based on the value R λ1,λ2 that indicates a diabetic risk indicator; and
transmitting the diabetic risk indicator to a remote device.
21. The biosensor of claim 1 , wherein the biosensor is further configured to:
determine a position of the biosensor, wherein the position of the biosensor includes at least one area of a body of the patient; and
adjust operation of the PPG circuit in response to the position of the biosensor.
22. The biosensor of claim 21 , wherein the processing circuit is configured to determine a position of the biosensor by:
obtaining a spectral response of underlying tissue from the PPG circuit;
detecting one or more characteristics of the underlying tissue from the spectral response;
correlating the detected one or more characteristics of the underlying tissue with predetermined characteristics of underlying tissue from a plurality of body areas, wherein the plurality of body parts include at least: an abdominal area, wrist, forearm, leg, earlobe or ear canal; and
determining the at least one area of the body of the patient on which the biosensor is located based on the correlation.
23. The biosensor of claim 22 , wherein the biosensor is configured to adjust the operation of the PPG circuit in response to the position of the biosensor by:
adjusting a wavelength to transmit to obtain a spectral response to detect a concentration level of a substance in response to the underlying tissue.
24. The biosensor of claim 22 , wherein the biosensor is configured to adjust the operation of the PPG circuit in response to the position of the biosensor by:
adjusting an absorption coefficient when determining a concentration level of a substance in response to the underlying tissue.