The technology paradigm for the Hemedex perfusion measuring system, called the Bowman Perfusion Monitor System, consists of a minimally invasive microprobe (Click HERE to view), appropriate insertion hardware for facilitating placement of the probe into the target tissue, an umbilical cable to connect the probe to the monitor, and a microprocessor-controlled, electronic monitor to collect, store, and display the perfusion data. The insertion hardware will be packaged together in the form of a kit, and will include devices necessary to secure the probe in place, and minimize the risk of infection.

This platform technology will greatly benefit numerous clinical situations where specific, quantitative knowledge of blood flow and oxygen delivery, in real time, is crucial.

What is Perfusion?
Tissue blood flow, often called perfusion, can be defined as the rate at which the quantity of blood in a given mass or volume of tissue is replenished at the level of the capillary network. Perfusion is a primary factor in the local transport of oxygen, nutrients, waste products, heat, and drugs.

Why is it important?
The ability to measure perfusion has been sought for many years, as this fundamental parameter holds the key to an improved understanding of both normal and pathologic physiology as well as the diagnosis and management of numerous medical situations including shock and tissue viability subsequent to traumatic injury, transplantation and non-surgical treatments of cancer.

How is perfusion otherwise measured?
While the overall importance of blood flow to human health has led to many techniques being proposed and/or pursued to quantify perfusion, many of these do not lend themselves to routine clinical application. Such techniques include: radioactive tracer washout techniques; positron emission tomography (PET); magnetic resonance imaging (MRI); radioactive microspheres; and laser-Doppler flowmetry (LDF). PET uses short half-life isotopes, requiring a special facility; while MRI, due to its numerous other medical applications, may hold future promise as a qualitative measure of perfusion. In any case, PET and MRI are complex, expensive and do not permit routine monitoring. Radioactive microspheres are suitable for perfusion validation studies in animal models, but are not appropriate for clinical measurements.

LDF can provide continuous monitoring; however, the signal depends on a number of factors such as hematocrit, red blood cell velocity, vascular geometry, and tissue optical properties, which vary according to tissue type. Thus, it is not currently possible to apply the LDF calibration and measurements from one tissue type to another tissue type. Further, it is unlikely that LDF units can be converted to absolute blood flow in all tissues. LDF may be useful, however, in validating perfusion variation for comparison to other measurement techniques. Thus, there is no other technique available that can monitor tissue perfusion continuously and in real time.

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• Overview
• Bowman Perfusion Monitor
• Bibliography