Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Reexamination Certificate
2000-05-08
2003-12-09
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
C600S310000
Reexamination Certificate
active
06662031
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to devices and methods for the noninvasive determination of concentrations of hemoglobin and hematocrit in a human subject in vivo, particularly for the noninvasive determination of concentrations of hemoglobin and hematocrit in a human subject in vivo, where the temperature of a defined subcutaneous volume of a body part of the subject is controlled and varied between preset boundaries.
2. Discussion of the art
Non-invasive (hereinafter “NI”) monitoring of analytes in the human body by optical devices and methods is an important tool in clinical diagnostics. NI monitoring techniques, which do not require obtaining a sample from the human body or inserting any instrumentation into the human body, have several advantages, including, but not limited to, ease of performing tests, reduction of pain and discomfort to the patient, and decreased exposure to potential biohazards.
The most established non-invasive optical technique is pulse oximetry. Oxygenation of blood in tissue and cerebral oxygen saturation can be measured, and the measurement can be used for clinical applications. See Jobsis, “Non-invasive, Infrared Monitoring of Cerebral and Myocardial Oxygen Sufficiency and Circulatory Parameters”,
Science
, 198, 1264-67 (1977), and Shiga, et al., “Study of an Algorithm Based on Model Experiments and Diffusion Theory for a Portable Tissue Oximeter”,
J. Biomed. Optics
; 2(2), 154-161 (1997).
Hemoglobin is the protein that transports oxygen. The hematocrit value provides an indication of the hemodynamics of the body. Non-invasive determination of the hemoglobin concentration (Hb) and the hematocrit value (Hct), when available, can be useful in blood donation centers, intensive care units, and surgical operation rooms. Non-invasive determination of the hemoglobin concentration and the hematocrit value can potentially be applied for diagnosis of anemia in infants and mothers, for localizing tumors, and for diagnosis of hematoma and internal bleeding. See S. Gopinath, et al., “Near-infrared spectroscopic localization of intracamerial hematomas”,
J. Neurosurgery
, 79, 43-47 (1993).
Concentration of hemoglobin and the ratio of oxygenated hemoglobin to total hemoglobin in blood are important parameters for indicating the anemic state and wellness of a patient. Hemoglobin is a protein having a molecular weight of 64,500 daltons; thus, 1 gram of hemoglobin is equivalent to 1.55×10
−5
mole. The concentration of hemoglobin is expressed in g/dL. The hematocrit value is the ratio of volume of red blood cells to total blood volume, which comprises the volume of red blood cells and the volume of plasma. The hematocrit value is expressed as a percentage (i.e., volume percentage of red cells in whole blood). While measurement of concentration of hemoglobin provides an indication of the oxygen transport status of the patient, measurement of the hematocrit value provides an indication of concentration of both red blood cells for transport of oxygen and plasma for transport of nutrients. The measurement of the hematocrit value is particularly important when a change in body hemodynamics is expected, such as during operations of long duration, such as, for example, vascular and orthopedic surgery. Other applications of hematocrit measurement include the treatment of hemorrhage in accident victims and the monitoring of cancer patients undergoing chemotherapy. Yet another application of hematocrit measurement involves monitoring kidney dialysis patients to reduce the potential for incomplete dialysis or excessive dialysis of the patient. Incomplete dialysis leaves toxins behind. Excessive dialysis leads to shock.
The standard method currently used for measuring hematocrit value is an invasive method. Typically, a blood sample is obtained from a patient or a donor and centrifuged in a capillary tube to separate red blood cells from plasma. The length of the column in the capillary tube containing red blood cells and the total length of the column in the capillary tube containing both the red blood cells and the plasma are measured, and the ratio of these lengths is the hematocrit value (Hct). Other methods for determining the hematocrit value involve the use of a flow cytometer, where a known volume of blood is injected in a fluid stream and the number of red blood cells (RBC) and their mean volume is determined. The total volume of RBC is calculated and the hematocrit value is determined from the volume of the sample and the total RBC volume. Hemoglobin concentrations can be determined in vitro by a photometric method, where a blood sample is hemolyzed and the heme moiety is released from hemoglobin at a high pH condition. The absorption of this heme moiety is determined at wavelengths of 577 nm and 633 nm.
U.S. Pat. No. 5,227,181, U.S. Pat. No. 5,553,615, and U.S. Pat. No. 5,499,627 describe hematocrit monitoring devices that involve the use of light of a limited number of wavelengths. These patents do not involve a non-invasive measurement or an apparatus having a means for controlling the temperature of a sample. Because the spectral and optical properties of samples of human tissue depend on temperature in the near infrared region of the electromagnetic spectrum, hematocrit and blood oxygenation measurements in this region of the electromagnetic spectrum can be inaccurate, when temperature is not controlled. Zhang et al., “Investigation of Non-invasive in Vivo Blood Hematocrit Measurement Using NIR Reflectance Spectroscopy and Partial Least-Squares Regression”, Applied Spectroscopy, vol. 54, no. 2, 294-299 (2000), discloses a method for non-invasively determining the hematocrit value in vivo during cardiac bypass surgery by employing a large number of wavelengths in the near-infrared region of the electromagnetic spectrum. Temperature of the patient was found to change during surgery. A high number of wavelengths and a partial least squares regression analysis were used in an effort to minimize the effect of temperature on the hematocrit value during the determination. Although the device and method described by Zhang et al. provide good calibration and prediction for a given patient during surgery, establishing a model to predict the hematocrit values across more than one patient was less successful. Systematic bias between patients was observed.
The effect of temperature on the scattering and absorption properties of tissue has been of interest in the art of non-invasive monitoring. Thermal effects of laser excitation, photocoagulation, and temperature effect on skin optics have been described in the art. See, for example, W-C. Lin et al., “Dynamics of tissue reflectance and transmittance during laser irradiation”, SPIE Proceedings, 2134A Laser-Tissue Interaction V, 296-303 (1994); and W-C. Lin, “Dynamics of tissue optics during laser heating of turbid media”, Applied Optics, Vol. 35, No. 19, 3413-3420 (1996). Other publications include J. Lauferet al., “Effect of temperature on the optical properties of ex vivo human dermis and subdermis”, Phys. Med. Biol. 43 (1998) 2479-2489; and J. T. Bruulsema et al., “Optical Properties of Phantoms and Tissue Measured in vivo from 0.9-1.3 &mgr;m using Spatially Resolved Diffuse Reflectance”, SPIE Proceedings 2979, 325-334 (1997).
U.S. Pat. Nos. 3,628,525; 4,259,963; 4,432,365; 4,890,619; 4,926,867; 5,131,391; and European Patent Application EP 0472216 describe oximetry probes having heating elements designed to be placed against a body part. U.S. Pat. No. 5,148,082 describes a method for increasing the blood flow in a patient's tissue during a photoplethysmography measurement by heating the tissue with a semiconductor device mounted in a sensor. U.S. Pat. No. 5,551,422 describes a glucose sensor that is brought to a specified temperature, preferably somewhat above normal body-temperature, with a thermostatically controlled heating system.
U.S. application Ser. No. 09/080,470, filed May 18, 1998, assigned to the assignee of this application, and WO 99/59464 desc
Hanna Charles F.
Jeng Tzyy-Wen
Kantor Stanislaw
Khalil Omar S.
Wu Xiaomao
Abbott Laboratoies
Kremer Matthew
Weinstein David L.
Winakur Eric F.
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