System and method for monitoring nitric oxide levels using a non-invasive, multi-band biosensor
View Patent ↗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 such as Nitric Oxide may then be determined from the spectral responses.
1. A biosensor for monitoring nitric oxide (NO) of a patient in vivo, 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;
generate at least a second spectral response for light reflected around a second wavelength from the skin tissue of the patient;
a processing circuit 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 ; and
obtain a concentration level of nitric oxide using the value R λ1, λ2 and a calibration database, wherein the calibration database is used to correlate the value R λ1, λ2 and the concentration level of nitric oxide (NO).
2. The biosensor of claim 1 , further comprising at least one of:
a wireless transceiver configured to transmit the concentration level of nitric oxide to another device; or
a port for a wired connection to communicate the concentration level of nitric oxide to another device.
3. The biosensor of claim 1 , wherein the first wavelength has a high absorption coefficient for nitric oxide in arterial blood flow and is in a range of approximately 370 nm to 410 nm.
4. The biosensor of claim 3 , wherein the second wavelength has a lower absorption coefficient for nitric oxide in arterial blood flow.
5. The biosensor of claim 1 , wherein the calibration database includes a range of R λ1, λ2 values and correlated concentration levels of nitric oxide and wherein the calibration database is generated using nitric oxide level measurements obtained from a large sample population.
6. The biosensor of claim 5 , wherein the calibration database includes different correlations between the R values and NO concentration levels depending on the underlying skin tissue.
7. The biosensor of claim 1 , further configured to:
obtain a concentration level of one or more hemoglobin species; and
compensate for the concentration level of the one or more hemoglobin species to determine the value R λ1, λ2 .
8. The biosensor of claim 7 , wherein the concentration level of the one or more hemoglobin species is determined by:
analyzing spectral response of a plurality of wavelengths to determine differential absorption signals for each hemoglobin species; and
using a Beer-Lambert matrix equation for determining the concentration levels of the one or more hemoglobin species.
9. A method for monitoring nitric oxide (NO) of a patient in vivo, comprising:
obtaining at least a first spectral response for light reflected around a first wavelength from skin tissue of the patient;
obtaining at least a second spectral response for light reflected around a second wavelength from the skin tissue of the patient;
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 ; and
obtaining a concentration level of nitric oxide using the value R λ1, λ2 and a calibration database, wherein the calibration database correlates the value R λ1, λ2 and the concentration level of nitric oxide (NO).
10. The method of claim 9 , wherein the first wavelength has a high absorption coefficient for nitric oxide in arterial blood flow and is in a range of approximately 370 nm to 410 nm.
11. The method of claim 10 , wherein the second wavelength has a lower absorption coefficient for nitric oxide in arterial blood flow.
12. The method of claim 9 , wherein the calibration database includes a range of R λ1, λ2 values and correlated concentration levels of nitric oxide and wherein the calibration database is generated using nitric oxide level measurements obtained from a large sample population.
13. The method of claim 12 , wherein the calibration database includes different correlations between the R values and NO concentration levels depending on the underlying skin tissue.
14. The method of claim 9 , further comprising:
obtaining a concentration level of one or more hemoglobin species; and
compensating for the concentration level of the one or more hemoglobin species to determine the value R λ1, λ2 .