Vascular oximetry system
A method for determining a hemoglobin saturation of a volume-oscillating vascular compartment in tissue includes receiving data representing measurements of a number of oscillating hemoglobin concentrations from the tissue and determining the hemoglobin saturation of the volume-oscillating vascular compartment to exclude an effect of an oscillating rate of supply of oxygenated blood to a portion of the tissue including removing a first contribution on one or more of the oscillating hemoglobin concentration measurements from at least one of the measurements, the first contribution being phase offset relative to said measurements.
1. A method for using a computer-implemented computational model to determine a hemoglobin saturation of a volume-oscillating vascular compartment in tissue with a non-negligible oscillating rate of supply of oxygenated blood to a portion of the tissue, the method including
receiving data representing measurements of a plurality of oscillating hemoglobin concentrations from the tissue;
receiving a representation of a phase offset between an oscillating oxygenated hemoglobin concentration measurement and an oscillating deoxygenated hemoglobin concentration measurement caused by an oscillating rate of supply of blood to the portion of the tissue, wherein the representation of the phase offset is either empirically derived or inferred using a coherent hemodynamics spectroscopy model; and
using the representation of the phase offset to determine the hemoglobin saturation of the volume-oscillating vascular compartment to exclude an effect on the determined hemoglobin saturation of an oscillating rate of supply of oxygenated blood to the portion of the tissue by removing a contribution of the oscillating rate of supply of blood from the oscillating oxygenated hemoglobin concentration measurement, and
providing the determined hemoglobin saturation for use in a medical setting;
wherein the computer implemented computational model relates the effect of the oscillating rate of supply of oxygenated blood to the portion of the tissue to an oscillation in the measured concentration of oxygenated hemoglobin and an oscillation in the measured concentration of deoxygenated hemoglobin due to oscillations in blood flow to the portion of the tissue.
2. The method of claim 1 wherein the plurality of oscillating hemoglobin concentrations from the tissue include a measured concentration of oxygenated hemoglobin, a measured concentration of deoxygenated hemoglobin, and a total hemoglobin concentration.
3. The method of claim 1 wherein the plurality of oscillating hemoglobin concentrations oscillate at a frequency associated with a physiological function.
4. The method of claim 3 wherein the plurality of oscillating hemoglobin concentrations oscillate at a cardiac frequency.
5. The method of claim 3 wherein the plurality of oscillating hemoglobin concentrations oscillate at a respiratory frequency.
6. The method of claim 1 wherein the plurality of oscillating hemoglobin concentrations oscillate at a physically induced frequency.
7. The method of claim 1 wherein the oscillation in the measured concentration of oxygenated hemoglobin and the oscillation in the measured concentration of deoxygenated hemoglobin are at least in part due to diffusion of oxygen from blood to the portion of the tissue.
8. The method of claim 1 wherein the portion of the tissue includes a capillary compartment of the tissue.
9. The method of claim 1 wherein the volume-oscillating vascular compartment includes an arterial compartment.
10. The method of claim 1 wherein the volume-oscillating vascular compartment includes a venous compartment.
11. The method of claim 1 wherein the volume-oscillating vascular compartment includes a mixture of an arterial compartment and a venous compartment.
12. The method of claim 11 further comprising determining a first fraction of the hemoglobin saturation associated with the venous compartment and a second fraction of the hemoglobin saturation associated with the arterial compartment.
13. The method of claim 12 wherein the second fraction of the hemoglobin saturation is determined based on a blood pressure measurement.
14. The method of claim 12 wherein the first fraction and the second fraction are determined based on an empirically determined ratio.
15. The method of claim 1 wherein the hemoglobin saturation of the volume-oscillating vascular compartment is determined at least in part using a multi-compartment hemodynamic model.
16. A system for determining a hemoglobin saturation of a volume-oscillating vascular compartment in tissue with a non-negligible oscillating rate of supply of oxygenated blood to a portion of the tissue, the system including
a first input for receiving data representing measurements of a plurality of oscillating hemoglobin concentrations from the tissue;
a second input for receiving a representation of a phase offset between an oscillating oxygenated hemoglobin concentration measurement and an oscillating deoxygenated hemoglobin concentration measurement caused by an oscillating rate of supply of blood to the portion of the tissue, wherein the representation of the phase offset is either empirically derived or inferred using a coherent hemodynamics spectroscopy model; and
an oximetry processing module including a computer implemented computational model for using the representation of the phase offset to determine the hemoglobin saturation of the volume-oscillating vascular compartment to exclude an effect on the determined hemoglobin saturation of an oscillating rate of supply of oxygenated blood to the portion of the tissue by removing a contribution of the oscillating rate of supply of blood from the oscillating oxygenated hemoglobin concentration measurement; and
an output for providing the determined hemoglobin saturation for use in a medical setting;
wherein the computer implemented computational model relates the effect of the oscillating rate of supply of oxygenated blood to the portion of the tissue to an oscillation in the measured concentration of oxygenated hemoglobin and an oscillation in the measured concentration of deoxygenated hemoglobin due to oscillations in blood flow to the portion of the tissue.
17. The system of claim 16 further comprising a sensor for obtaining the data representing measurements of the plurality of hemoglobin concentrations from the tissue and providing the data to the first input.
18. The system of claim 16 further comprising a display device for receiving a representation of the determined hemoglobin saturation of the volume-oscillating vascular compartment from the output and presenting the representation of the determined hemoglobin saturation of the volume-oscillating vascular compartment.
19. The system of claim 16 wherein the oximetry processing module determines the hemoglobin saturation of the volume-oscillating vascular compartment is determined at least in part using a multi-compartment hemodynamic model.