Optical and ultrasound probe for monitoring blood volume changes
First Claim
1. A process for monitoring changes in blood volume and microvascular pooling in animals, comprising:
- an extracorporeal blood treatment device in which blood from a blood system is conducted through a first branch of said extracorporeal system which is connected by tubing to an arterial segment of said blood system into a dialyzer or filter and returned via a second branch of said extracorporeal system with the said second branch connected by tubing to a venous segment of said blood system;
a diagnostic apparatus attached to said tubing wherein said diagnostic apparatus emits and receives an ultrasound wave and a light wave through blood flowing through said extracorporeal system;
a signal processing system, wherein said signal processing system initiates and records ultrasound waves and light transmissions, determines phase shift between emitting and receiving ultrasound waves, monitors with high resolution sound velocity, density, compressibility, and optical density of blood, hematocrit, and plasma protein concentration, and assesses changes in said sound velocity, density, compressibility, optical density, hematocrit, and plasma protein concentration of modified blood at an equivalent temperature an infusion system, wherein a known amount of an indicator fluid is infused into said blood system at an injection connection located downstream of said diagnostic apparatus, and wherein infusion of said indicator fluid into said blood system changes the density of said blood system as measured through said diagnostic apparatus and said signal processing system;
a calibration procedure; and
a computing system for determining blood volume, changes in blood volume, changes in plasma protein concentration, and microvascular pooling from said hematocrit and density change.
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Abstract
An apparatus and method to assess the compressibility, density, and hematocrit of blood including an optical ultrasound probe clipped onto tubing in which blood is flowing. The probe includes a combination of ultrasound transducers, a light emitting diode, and photodiodes. An indicator medium is injected into the bloodstream of the subject over one or more time points. Ultrasound waves are emitted by a transducer and received by another transducer, and a novel signal-processing unit and a computer with a novel computation scheme process the ultrasound signals to assess the phase shift of ultrasound as it transmitted across the blood stream. Based on the linear relationship between compressibility and density, changes in blood density are calculated from changes in phase shift. The optical part of the probe assesses the hematocrit of blood. Two fluid media are used to calibrate the probe on the relationship between phase shift and density in the factory. Before clinical assessment, an on-line saline injection procedure and the resulting change in density is employed to calibrate the optical density of the optical probe in terms of hematocrit and to establish the interrelation between density and hematocrit on fluid dilution of the circulating blood. One clinical protocol to monitor blood volume and microvascular pooling employs saline infusion to determine the blood volume hourly and the density and hematocrit measurements to determine the change in blood volume and the volume pooled to the microcirculation. Another clinical protocol assesses the time course of hematocrit and density over hemodialysis treatment for the prediction of hypovolemia and microvascular pooling. This cardiovascular monitoring is useful for evaluating how complications are developed during hemodialysis or the adequacy of any post-trauma fluid replacement or therapy to alleviate the complications.
33 Citations
21 Claims
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1. A process for monitoring changes in blood volume and microvascular pooling in animals, comprising:
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an extracorporeal blood treatment device in which blood from a blood system is conducted through a first branch of said extracorporeal system which is connected by tubing to an arterial segment of said blood system into a dialyzer or filter and returned via a second branch of said extracorporeal system with the said second branch connected by tubing to a venous segment of said blood system;
a diagnostic apparatus attached to said tubing wherein said diagnostic apparatus emits and receives an ultrasound wave and a light wave through blood flowing through said extracorporeal system;
a signal processing system, wherein said signal processing system initiates and records ultrasound waves and light transmissions, determines phase shift between emitting and receiving ultrasound waves, monitors with high resolution sound velocity, density, compressibility, and optical density of blood, hematocrit, and plasma protein concentration, and assesses changes in said sound velocity, density, compressibility, optical density, hematocrit, and plasma protein concentration of modified blood at an equivalent temperature an infusion system, wherein a known amount of an indicator fluid is infused into said blood system at an injection connection located downstream of said diagnostic apparatus, and wherein infusion of said indicator fluid into said blood system changes the density of said blood system as measured through said diagnostic apparatus and said signal processing system;
a calibration procedure; and
a computing system for determining blood volume, changes in blood volume, changes in plasma protein concentration, and microvascular pooling from said hematocrit and density change. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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- 13. A method for monitoring a patient'"'"'s cardiovascular function through use of an optical ultrasound probe.
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17. A process for monitoring changes in blood volume and microvascular pooling in animals, comprising:
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a diagnostic apparatus attached to a blood system wherein said diagnostic apparatus emits and receives an ultrasound wave and a light wave through blood flowing through an extracorporeal system;
a signal processing system, wherein said signal processing system determines a phase shift between said emitting and receiving ultrasound wave, and determines absorbance and reflectance of said light wave;
at least two control units within said signal processing system for detecting compressibility, density, hematocrit and plasma protein concentration with high resolution, for assessing changes in said compressibility, density, hematocrit, and plasma protein concentration at an equivalent temperature, for initiating and recording ultrasound and light waves, and for monitoring physical parameters of modified blood; and
a computer memory unit for determining blood volume and microvascular pooling from said hematocrit and density change. - View Dependent Claims (18, 19, 20, 21)
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Specification