Hematocrit measurement by differential optical geometry in a short-term diagnostic cardiovascular catheter, and application to correction of blood-oxygen measurement
First Claim
1. A system for determining the corpuscular content of a fluid that contains a varying quantity of corpuscles, comprising:
- means, remote from such fluid, for emitting light;
means, remote from such fluid, for detecting light;
optical-fiber means for transmitting light from the remote light-emitting means via such fluid to the remote light-detecting means along two paths, each of said two paths including two segments;
a first optical-fiber-means segment for directing light from the remote emitting means to such fluid, terminating in light-projecting means disposed adjacent to such fluid,a second optical-fiber-means segment, commencing in light-receiving means disposed adjacent to such fluid, for directing light from such fluid to the remote detecting means after scattering by such fluid and by such corpuscles therein;
the first segment and its light-projecting means for one of the two paths having a first fixed, known geometrical relationship to the second segment and its light-receiving means for that one path;
the first segment and its light-projecting means for the other of the two paths having a second fixed, known geometrical relationship to the second segment and its light-receiving means for that other path;
said second geometrical relationship being different from said first geometrical relationship; and
interpretation means, responsive to the light-detecting means, for comparing the light respectively transmitted along the two paths, to determine such quantity of corpuscles, taking into consideration said known geometrical relationships.
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Accused Products
Abstract
An optical fiber carries a light beam through a cardiovascular catheter and projects the beam into the patient'"'"'s bloodstream. Two other fibers, spaced in a very carefully controlled configuration from the first, receive light scattered by corpuscles (and blood-vessel walls) and transmit this reflected light back through the catheter to respective detectors outside the patient'"'"'s body. If preferred, two input fibers and a single output fiber--or other techniques for providing differential geometry--may be used instead. Electronic instrumentation finds the ratio of the two light fluxes, thus cancelling out unknown variables such as input light intensity and optical--connector attenuation. The known differential geometry between the two light paths permits calibration of the ratio measurement in terms of corpuscular concentration--i.e., hematocrit. Light at only one wavelength suffices for the measurement. Advanced forms of the invention correct for proximity of blood-vessel walls. This system is particularly compatible with optical-fiber measurements of oxygen saturation, as either or both of the light paths already provided may be used for the oxygen reflectometry.
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Citations
16 Claims
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1. A system for determining the corpuscular content of a fluid that contains a varying quantity of corpuscles, comprising:
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means, remote from such fluid, for emitting light; means, remote from such fluid, for detecting light; optical-fiber means for transmitting light from the remote light-emitting means via such fluid to the remote light-detecting means along two paths, each of said two paths including two segments; a first optical-fiber-means segment for directing light from the remote emitting means to such fluid, terminating in light-projecting means disposed adjacent to such fluid, a second optical-fiber-means segment, commencing in light-receiving means disposed adjacent to such fluid, for directing light from such fluid to the remote detecting means after scattering by such fluid and by such corpuscles therein; the first segment and its light-projecting means for one of the two paths having a first fixed, known geometrical relationship to the second segment and its light-receiving means for that one path; the first segment and its light-projecting means for the other of the two paths having a second fixed, known geometrical relationship to the second segment and its light-receiving means for that other path;
said second geometrical relationship being different from said first geometrical relationship; andinterpretation means, responsive to the light-detecting means, for comparing the light respectively transmitted along the two paths, to determine such quantity of corpuscles, taking into consideration said known geometrical relationships. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A system for determining the corpuscular content of a fluid that contains a varying quantity of corpuscles, comprising:
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a light source that is remote from such fluid; two light detectors that are both remote from such fluid; a first optical fiber having a proximal end outside and remote from such fluid and disposed to receive light from the source, and having a distal end, from which the proximal end is remote, that is adapted to be juxtaposed to such fluid so as to project the light into such fluid; second and third optical fibers, each having a distal end that is; in fixed, known geometric relationship to the distal end of the first fiber, and adapted to be juxtaposed to such fluid to receive a respective portion of the light projected by the first fiber, after scattering by such fluid; the second and third optical fibers also each having a proximal end that is remote from the respective distal end, and is outside and remote from such fluid, and is disposed to project its received portion of light to a respective one of the detectors; the geometric relationships of the second and third optical-fiber distal ends with the first optical-fiber distal end being different from one another; and interpretation means for comparing the light projected to the two detectors to determine such quantity of corpuscles, taking into consideration said known geometric relationships between the distal ends of the fibers. - View Dependent Claims (10, 11, 12)
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13. A system for determining the corpuscular content of a fluid that contains a varying quantity of corpuscles, comprising:
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two light sources that are both remote from such fluid; one light detector that is remote from such fluid; a first optical fiber having a distal end adapted to be juxtaposed to such fluid so as to receive light scattered from such fluid, and having a proximal end that is remote from the distal end and is outside and remote from such fluid and disposed to project the received light to the remote detector; second and third optical fibers, each; having a proximal end outside and remote from such fluid and disposed to receive respective light from a respective one of the remote sources, and having a distal end, from which the respective proximal end is remote, that is in fixed, known geometric relationship to the distal end of the first fiber; the distal ends of the second and third optical fibers being adapted for juxtaposition to such fluid to project into such fluid the light respectively received from the respective remote source; the geometric relationships of the second and third optical-fiber distal ends with the first optical-fiber distal end being different from one another; and interpretation means for comparing the light projected to the remote detector to determine such quantity of corpuscles, taking into consideration said known geometric relationships between the distal ends of the fibers. - View Dependent Claims (14, 15, 16)
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Specification