Non-invasive method and system of optical measurements for determining the concentration of a substance in blood

A non-invasive method of optical measurements for determining concentration of at least one substance in the patient's blood, the method comprising the steps of:

• (a) applying an over-systolic pressure to the patient's blood perfused fleshy medium with a normal blood flow at a first location on the patient's body, such as to cause a state of temporary blood flow cessation at a second location on the patient's body located downstream of said first location with respect to a normal blood flow direction for a cessation time period being insufficient for irreversible changes in the fleshy medium.
• (b) releasing the over systolic pressure at the first location to cause a state of transitional blood flow terminating with the normal blood flow at the second location;
• (c) selecting at least two timely separated sessions for performing the optical measurements on the blood perfused fleshy medium at said second location, wherein the selected sessions are such that light response of the medium at said at least two sessions substantially differs from each other, at least one of said at least two sessions being selected within a time period including the state of temporary blood flow cessation and the state of transitional blood flow;
• (d) effecting the optical measurements at said at least two sessions successively, each session including illumination of said second location with first and second wavelengths of incident light, and detection of first and second light responses of the medium;
• (e) determining a logarithm of the detected light response at the first wavelength as a function of a logarithm of the detected light response at the second wavelength;
• and
• (f) determining the concentration as a parametric slope of said function.

An optical measurement system for non-invasive determination of concentration of at least one substance in the patient's blood, the system comprising:

• (a) a pressurizing assembly operable for applying an over-systolic pressure to the blood perfused fleshy medium with the normal blood flow at a first location on the patient's body to thereby create a state of temporary blood flow cessation at a second location on the body downstream of said first location with respect to a normal blood flow direction, while substantially not affecting blood volume at the second location;
• (b) an illumination-detection arrangement operable to illuminate the medium at said second location with at least two different wavelengths of incident light, detect light responses of the illuminated medium and generate data representative thereof;
• and
• (c) a control unit interconnected between said illumination-detection arrangement and said pressurizing assembly, wherein
• said control unit operates the presurizing assembly so as to selectively apply the over-systolic pressure to the first location and thereby create the state of temporary blood flow cessation at the second location, maintain the over systolic pressure at the first location for a cessation time period being insufficient for irreversible changes in the fleshy medium, and release the over systolic pressure at the first location to create a state of transitional blood flow terminating with the normal blood flow at said second location;
• and
• said control unit operates the illumination-detection arrangement to perform the optical measurements during at least two timely separated measurement sessions, each with said at least two different wavelengths of the incident light, the measurement sessions being selected such that the light responses of the medium to the incident light of the same wavelength at said at least two sessions substantially differ from each other, and at least one of said at least two sessions is selected within a time period including the state of temporary blood flow cessation and the state of transitional blood flow;
• said control unit is responsive to said data representative of the detected light responses to define measurement results in the form of the at least two light responses as different functions of time corresponding to the at least two different wavelengths, respectively, and to analyze the measurement results and determine relation between the two functions indicative of the concentration of said at least one substance of the blood.

A non-invasive method of optical measurements for determining concentration of at least one substance in patient's blood, the method comprising the steps of:

• (a) applying an over-systolic pressure to the patient's blood perfused fleshy medium with a normal blood flow at a first location on the patient's body, thereby creating a state of temporary blood flow cessation at a second location on the body downstream of the first location with respect to a normal blood flow direction, while substantially not affecting blood volume at the second location, and maintaining the pressure to maintain the blood flow cessation state for a cessation time period being insufficient for irreversible changes in the fleshy medium;
• (b) releasing the over systolic pressure at the first location thereby creating a state of transitional blood flow terminating with the normal blood flow at the second location;
• (c) selecting at least two timely separated sessions for the optical measurements at said second location, wherein the selected sessions are such that light responses of the medium to incident light of the same wavelength at said at least two sessions substantially differ from each other, at least one of said at least two sessions being selected within a time period including the state of temporary blood flow cessation and the state of transitional blood flow;
• (d) performing the optical measurements at said at least two sessions at said second location, each session including illumination of the second location with at least two different wavelengths of incident light and detection of light responses of the medium, thereby obtaining measurement results in the form of at least two light responses of the medium as different functions of time corresponding to said at least two wavelengths, respectively;
• and
• (e) analyzing the measurement results to determine relation between the two time functions indicative of the concentration of said at least one substance.