Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Reexamination Certificate
1997-05-20
2001-01-23
Nasser, Robert L. (Department: 3736)
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
C600S473000
Reexamination Certificate
active
06178342
ABSTRACT:
1. TECHNICAL FIELD
The present invention relates to a blood perfusion monitor which may be used to determine the skin perfusion pressure of a portion of a patient body such as a limb. The apparatus is used to determine the applied pressure which corresponds to the cessation or resumption of localized blood flow in the limb or other anatomic structure.
2. BACKGROUND
Laser Doppler blood flow monitors have been used in conjunction with pneumatic cuffs to determine localized blood flow see for example
The Correlation between Three Methods of Skin Perfusion Measurement
(J. Vasc Surg 1992;15:823-30). Laser Doppler blood flow monitors are known from U.S. Pat. No. 4,596,254 among others. Devices of this type use a fiber optic wave guide to scatter coherent light off of both, moving particles, mainly red blood cells (RBC), and stationary vascular structures. The back scattered radiation is conducted by a separate fiber optic wave guide to a photodetector. The back scattered laser light returned to the photodetector is frequency shifted by the moving particles in accordance with the Doppler effect. Consequently the photodetector signal includes an AC signal component related to the number of RBC and their velocity. This AC signal is superimposed on a DC offset signal which depends in part on the intensity of the coherent light source and the geometry of the multiple fiber detector. Blood volume or hematocrit information and blood velocity information can be extracted from the composite photodetector signal.
Blood flow information is computed by multiplying the blood velocity data by the blood volume data. One problem with the use of flow monitors for perfusion measurements or studies is that the blood flow product value is very sensitive to small errors in measured blood velocity or measured blood volume. This property of flow measurement makes the technique problematical for monitoring skin perfusion pressure.
SUMMARY
By contrast, the perfusion pressure monitor of the present invention does not measure blood flow itself. The perfusion pressure monitor of the present invention measures the “amount” of moving blood contained within a microvascular observation volume in percent tissue hematocrit. This percent hematocrit measurement is taken as a function of applied pressure. The optical probe defines an observation volume in the skin near the surface of the patient. A pressure cuff is used to apply pressure to the patient near the optical probe.
The skin perfusion pressure measurement involves the measurement of the pressure within the cuff at the moment that blood within the observation volume is either stationary or expressed from the observation volume. The pressure corresponding to the change in effective percent hematocrit is a significant diagnostic indication for many medical procedures.
REFERENCES:
patent: 4596254 (1986-06-01), Adrian et al.
patent: 4597393 (1986-07-01), Yamakoshi et al.
patent: 4927264 (1990-05-01), Shiga et al.
patent: 5111817 (1992-05-01), Clark et al.
patent: 5277181 (1994-01-01), Mendelson
“The Correlation Between Three Methods of Skin Perfusion Pressure Measurement: Radionuclide Washout, Laser Doppler Flow, and Photoplethysmography”, Leopoldo Malvezzi, MD, John J. Castronuovo, Jr., MD, Lawrence C. Swayne, MD, David Cone, BA, and Jessie Z. Trivino, MS, Morristown, N.J.,Journal of Vascular Surgery, pp. 823-830, vol. 15, No. 5, May, 1992.
“Laser-Doppler Flowmetry A Review of Its Application for Measuring Cerebral and Spinal Cord Blood Flow”, Kai U. Frerichs and Giora Z. Feuerstein,Molecular and Chemical Neuropathology, pp. 55-69, vol. 12, 1990 by the Human Press Inc.
“Microvascular Blood Flow Measurement by Laser Doppler Flowmetry”, Daniel J. Haumschild, Ph.D, Medical Instruments Group, TSI Incorporated, St. Paul, MN,TSI Application Note.
“TSI's LDV Blood Flowmeter”, John A. Borgos.
“Model for Laser Doppler Measurements of Blood Flow in Tissue”, R. Bonner and R. Nossal,Applied Optics, pp. 2097-2107, vol. 20, No. 12, Jun. 15, 1991.
“In Vivo Evaluation of Microcirculation by Coherent Light Scattering”, M. D. Stern,Nature, pp. 56-58, vol. 254, Mar. 6, 1975.
“Blood-Flow Measurements of Injured Peripheral Nerves by Laser Doppler Flowmetry”, C. M. Barone, D. F. Jimenez and A. Frempog-Bodeau,Journal of Reconstructive Microsurgery, pp. 319-323, vol. 8, No. 4, Jul., 1992.
“Simultaneous Measurement of Skin Blood Flow by the Transient Termal-clearance Method and Laser Doppler Flowmetry”, M. Nitzan, S. L. E. Fairs and V. C. Roberts.
“Laser Doppler Flowmetry Evaluation of Burn Wound Depth”, T. J. O'Reilly, MD, R. J. Spence, MD, R. M. Taylor, MD and J. J. Scheulen, PA,The Journal of Burn Care&Rehabilitation, pp. 1-6, vol. 10, No. 1, Jan./Feb., 1989.
“Evaluation of Skin Blood Flow and Venoarteriolar Response in Patients with Diabetes and Peripheral Vascular Disease by Laser Doppler Flowmetry”, Gianni Belcaro, MD, Spiros Vasdekis, MD, Alexander Rulo, MD and Andrew N. Nicolaides, MSAngiology—The Journal of Vascular Diseases, pp. 953-957, vol. 40, No. 11, Nov., 1989.
“Combined Evaluation of Postphlebitic Limbs by Laserdoppler Flowmetry and Transcutaneous P02/PC02 Measurements”, Messmethoden—Diagnostic Methods, G. Belcaro, A. Rulo, S. Vasdekis, M. A. Williams and A. N. Nicolaides,VASA, Band 17, 1988, Heft 4.
“Laser-Doppler Assessment of Brain Microcirculation: Effect of Systemic Alterations”, Rowan L. Haberl, Marcia L. Heizer, Anthony Marmarou and Earl F. Ellis,The American Physiological Society, pp. H1247-H1254.
Borgos John A.
Thompson RIchard John
Nasser Robert L.
Vasamedics
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