Method for the measurement of oxygen concentration levels by the steady-state determination of fluorescence lifetime
First Claim
1. A method of measuring an oxygen concentration or partial pressure of a fluid comprising the steps of:
- (a) contacting the fluid with a sensor comprising a housing containing a lipid soluble fluorescent probe substance having a fluorescence lifetime (τ
) which is sensitive to quenching by oxygen, admixed in a nonpolar solvent;
(b) irradiating the fluorescent probe substance of step (a) within the sensor housing with continuous, linearly polarized ultraviolet light at wavelengths strongly absorbed by the fluorescent probe substance to emit fluorescence having vector components parallel and perpendicular to the plane of polarization of the ultraviolet light;
(c) resolving the emitted fluorescence of step (b) into vector components parallel and perpendicular to the plane of polarization of the ultraviolet light;
(d) calculating a fluorescence anisotropy in time of the fluorescence emitted by the fluorescent probe substance of step (a) within the sensor housing from the vector components of step (c) by applying a first mathematical function, the first mathematical function being in the form of a first equation; and
(e) applying a second mathematical function which relates fluorescence anisotropy to oxygen concentration or partial pressure, the second mathematical function being in the form of a second equation.
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Abstract
Methods are described for the in vivo topographic determination of tissue and bodily fluid oxygen concentration or PO2 within an imaged tissue, as well as a method for measuring blood or bodily fluid PO2 with a fiber optic catheter. In the first method, a lipid soluble, biocompatible fluorescent probe substance is administered to an animal body and accumulates within the lipid bilayers of its tissue cells. In the second method, the fluorescent probe substance is conjugated to a large molecular mass protein which causes it to be retained within a bodily fluid such as blood. In the third method describing a catheter design, in which PO2 is measured at the catheter tip, the tip contains the fluorescent probe substance dissolved in a viscous nonpolar solvent. In all methods described, a fluorescent probe substance is preferred whose fluorescence lifetime is quenched by molecular oxygen, and oxygen concentration or PO2 is determined by measuring the fluorescence anisotropy of the fluorescent probe substance. The bodily fluid or tissue containing the biocompatible fluorescent probe substance, or the fluorescent probe substance in a nonpolar solvent within a catheter tip, is irradiated with continuous linearly polarized ultraviolet light at a wavelength strongly absorbed by the fluorophore. The emitted fluorescence is resolved into its vector components parallel and perpendicular to the plane of polarization of the excitation light, thereby permitting the calculation of the fluorescence anisotropy of the irradiated specimen. Tissue and/or bodily fluid PO2 of the imaged specimen, or the PO2 of a fluid at the tip of a sealed catheter, is determined by applying a mathematical function which relates the fluorescence anisotropy of an O2 -quenchable fluorophore to oxygen concentration or partial pressure.
86 Citations
15 Claims
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1. A method of measuring an oxygen concentration or partial pressure of a fluid comprising the steps of:
-
(a) contacting the fluid with a sensor comprising a housing containing a lipid soluble fluorescent probe substance having a fluorescence lifetime (τ
) which is sensitive to quenching by oxygen, admixed in a nonpolar solvent;(b) irradiating the fluorescent probe substance of step (a) within the sensor housing with continuous, linearly polarized ultraviolet light at wavelengths strongly absorbed by the fluorescent probe substance to emit fluorescence having vector components parallel and perpendicular to the plane of polarization of the ultraviolet light; (c) resolving the emitted fluorescence of step (b) into vector components parallel and perpendicular to the plane of polarization of the ultraviolet light; (d) calculating a fluorescence anisotropy in time of the fluorescence emitted by the fluorescent probe substance of step (a) within the sensor housing from the vector components of step (c) by applying a first mathematical function, the first mathematical function being in the form of a first equation; and (e) applying a second mathematical function which relates fluorescence anisotropy to oxygen concentration or partial pressure, the second mathematical function being in the form of a second equation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification