Apparatus and method for using ultrasound to determine hematocrit

• US 4,854,170 A
• Filed: 10/12/1988
• Issued: 08/08/1989
• Est. Priority Date: 10/12/1988
• Status: Expired due to Term

• Current Assignee: Separation Technology, Inc.
• Original Assignee: Separation Technology, Inc.
• Inventors: Riddle, Merwyn D., Brimhall, Owen D., Baker, Charles D., Peterson, Stephen C.
• Primary Examiner(s): Noland, Tom
• Assistant Examiner(s): Arana, Louis M.
• Application Number:
  US07/256,731
• Time in Patent Office: 300 Days
• Field of Search: 73/570, 73/24, 73/61.4, 210/748, 356/40
• US Class Current: 73/570
• CPC Class Codes: B01D 21/283 Settling tanks provided with vibrators
• CPC Class Codes: G01N 33/491 by separating the blood components G01N15/05 takes precedence

Abstract

This invention is an ultrasound apparatus for determining hematocrit. A sample of blood in a microhematocrit capillary tube is acoustically coupled to an ultrasound transducer which creates a standing wave in the blood sample. Red blood cells in the blood sample are packed in bands that correspond to the nodes of the standing wave. The thickness of the bands as a function of the thickness of the remaining plasma is an indication of the hematocrit of the blood sample.

Claims

1. An apparatus for determining hematocrit comprising:

a microhematocrit capillary tube;

a blood sample in the microhematocrit capillary tube;

an ultrasound transducer for producing ultrasound energy;

a frequency generator means for generating a preselected frequency signal for the ultrasound transducer;

amplifier means for amplifying the frequency signal from the frequency generator and transmitting the amplified signal to the ultrasound transducer;

coupling means for coupling the ultrasound energy from the ultrasound transducer into the blood sample; and

a meniscus formed at the end of the blood sample, the meniscus forming a reflector for ultrasound energy in the blood sample thereby creating a standing wave in the ultrasound energy in the blood sample.

2. The apparatus defined in claim 1 wherein the ultrasound transducer includes a heat sink for dissipating heat generated in the ultrasound transducer by the amplified signal.

3. The apparatus defined in claim 1 wherein the microhematocrit capillary tube includes a plug and the plug comprises the coupling means.

4. An apparatus for using ultrasound to determine hematocrit comprising:

a microhematocrit capillary tube;

a sample of blood in the microhematocrit capillary tube, the sample of blood being drawn by capillary action into a first end of the microhematocrit capillary tube;

a meniscus in said sample of blood at a second end of the microhematocrit capillary tube;

an ultrasound transducer means for producing ultrasonic energy;

a frequency generator means for generating an ultrasound frequency signal for the ultrasound transducer;

an amplifier means for amplifying the ultrasound frequency signal from the frequency generator means and connector means for connecting the amplified ultrasound frequency signal into the ultrasound transducer to produce said ultrasonic energy;

coupling means for coupling the ultrasonic energy into the blood sample; and

reflector means in said blood sample for creating a standing wave in said blood sample, said reflector means comprising said meniscus, the meniscus reflecting the ultrasonic energy to create said standing wave in the blood sample.

5. The apparatus defined in claim 4 wherein the ultrasound transducer includes a heat sink for dissipating heat generated in the ultrasound transducer by the amplified signal.

6. The apparatus defined in claim 4 wherein the microhematocrit capillary tube includes a plug and the plug comprises the coupling means.

7. A method for using ultrasound to determine hematocrit comprising:

obtaining an ultrasound transducer;

providing an ultrasound frequency generator;

connecting an amplifier between the ultrasound frequency generator and the ultrasound transducer thereby amplifying for the ultrasound transducer a signal from the ultrasound frequency generator;

selecting a microhematocrit capillary tube;

drawing a sample of blood by capillary action into a first end of the microhematocrit capillary tube;

forming a meniscus in said sample of blood at a second end of the microhematocrit capillary tube;

ultrasonically coupling the first end of the microhematocrit capillary tube to the ultrasound transducer;

forming standing waves in the blood sample by transmitting ultrasound energy into the blood sample from the ultrasound transducer and reflecting the ultrasound energy by the meniscus, the standing waves banding the blood sample into bands of packed red blood cells separated by bands of plasma.