Contact:Edward Tate215-443-9406[email protected]
NEW DEVICE FOR TESTING HUMAN BLOOD UNVEILED IN SCIENTIFIC JOURNAL
Pharmaceutical and medical researchers will soon be able to measure for the first time the viscosity or thickness of unadulterated human blood with accuracy and ease using a new device reported in the August issue of the Review of Scientific Instruments.
"By measuring the physical parameters of blood flow and not just the chemical composition, we're opening the door to a radically different perspective on human disease, particularly atherosclerosis," says Kenneth R. Kensey, M.D., cardiologist and co-author of the journal article. "Medical science has focused almost exclusively on the chemical composition of blood, such as cholesterol and triglyceride levels. While blood chemistry is absolutely important, studies have shown that physical properties -- such as viscosity -- may play a critical role, and that has been largely overlooked."
Physical properties of blood directly affect blood flow, Dr. Kensey points out, and sufficient blood flow is essential for the health of all organs. Since blood supplies oxygen and nutrients needed for living cells and removes the cells' waste products, when blood flow is impeded in any way, medical problems arise, ranging from heart attacks and strokes to kidney disease and blindness. Perhaps the aging process in general is affected as well.
Among researchers who have studied blood viscosity is Gregory D. Sloop, M.D., associate professor at the Louisiana State University College of Medicine. "Indeed, increased viscosity is so pervasive in patients with atherosclerosis that it has been proposed to be one mechanism by which all major risk factors promote atherosclerosis," he wrote in a 1996 article in the journal Medical Hypotheses.
Viscosity's importance has been evaluated by the Edinburgh Artery Study, which since 1988 has followed nearly 1,500 adults older than 54 years. "Our results suggest that blood viscosity is as strong a predictor of cardiovascular events in the older population as (elevated) LDL cholesterol or (elevated) diastolic blood pressure, and is stronger than smoking; that it (viscosity) may be a stronger predictor of stroke than these conventional risk factors...," according to a 1997 report on the Edinburgh Study in the British Journal of Haemotology.
The primary advantage of the new viscometer described in this month's Review of Scientific Instruments is that it produces an accurate spectrum of viscosity data across a broad range of velocity changes.
"As blood moves at a high velocity during the systolic (pumping) phase, it behaves as a very thin fluid," according to Young I. Cho, Ph.D., co-author of the viscometer study and Drexel University professor of mechanical engineering. "During the diastolic phase (resting), blood moves very slowly, or almost zero velocity, and it becomes very thick."
For patients with elevated blood viscosity, the further thickening that occurs during the diastolic phase is a primary contributor to atherosclerosis, according to Dr. Kensey.
Instruments commonly used to measure the viscosity of human blood only measure at one or two velocities for each test cycle, says Prof. Cho, a widely published researcher who has been honored with two awards from NASA. He says that conventional viscometers do not generate useful data for low-pressure and low-velocity conditions.
The new viscometer links a laptop computer to an optical scanner and a closed system of tubing that contains the blood sample. Because the blood-handling system is entirely sealed and the tubing has a newly developed biocompatible coating, it does not require the use of an anticoagulant, such as heparin or EDTA, unlike older viscometers. By covering the tubing with materials similar to the cells that line arterial walls, the coating simulates in-vivo conditions and the patient's blood is never exposed to non-human materials. That is a distinct advantage, Prof. Cho says, since anticoagulants adulterate the blood and can produce unpredictable results. Since the blood-handling system is closed and composed of low-cost disposable tubing, there is minimal contamination risk to the operator and little cleanup effort required.
Another benefit of the new instrument is that testing begins seconds after a blood sample is drawn. The computer produces analyzed results in about four minutes at the patient's bedside.
Currently, blood is drawn and then the samples are taken to a laboratory for testing, which can take hours or days to process and complete, a period during which blood properties change due to temperature swings and aging.
Dr. Kensey developed the new instrument, with the assistance of a team he assembled, through Visco Technologies, Inc. of Exton, Pa., a company he founded three years ago. The device, which the developers describe as a scanning capillary tube viscometer, will be available by the end of this year or early in 2001. Viscosity is only one flow parameter that this device will measure. Numerous additional measures of the physical parameters of a patient's blood never before measured can be derived from data generated by the new device, including stickiness, slickness, abrasiveness and lubricity. Initially, pharmaceutical companies and medical researchers will be the primary targets for Visco Technologies' marketing efforts.
"We believe strongly that this valuable data will allow researchers to develop new applications and new patents for existing drugs," Dr. Kensey says. "The device will support efforts by pharmaceutical companies seeking to further differentiate their products from those of competitors.
"Additionally, this new device and the insights it produces will assist with development of new medications and play a role in further advancing medical research in a wide range of areas," Dr. Kensey says.
"My personal goal is to find ways to prevent heart attacks and strokes -- the number one and number three killers in the United States. Studying blood flow and being able to accurately measure the physical properties of blood that allow it to flow will soon allow us to develop treatments that make blood flow more easily. That will eliminate the adverse effects that thick, sticky blood has on our artery walls and on our bodies' cells in general."
One of Kensey's inventions, the AngioSeal (an arterial puncture closure device used following cardiac catheterizations), is now widely used around the world.
The Review of Scientific Instruments, a publication of the American Institute of Physics, can be accessed via the institute's website: www.aip.org. An abstract of the Kensey and Cho article, "A Scanning Dual-Capillary-Tube Viscometer," can be viewed on the site and a copy of the article can also be purchased.
The Visco Technologies website address is www.viscotech.com.
- 30 -
RSS