Chronic venous insufficiency - or CVI - is a very common medical condition in which veins in the legs cannot pump enough oxygen-poor blood back to the heart. It is caused by faulty valves within the leg veins, and causes blood to pool in the legs, which can lead to edemas and even open ulcers. Typically, treatment consists of anti-inflammatory drugs and diuretics, along with the use of items such as compression stockings. Now scientists have developed a method of mass-producing artificial venous valves, that could replace the malfunctioning natural ones.
The artificial valves are being developed by scientists at Germany's Fraunhofer Institute for Manufacturing Engineering and Automation. They are made from polycarbonate-urethane (PCU), a plastic that is strong yet flexible, can be formed into very thin layers, and is easy to sew into body tissue.
In the production process, a solvent containing dissolved PCU is deposited by a dispensing tool, one droplet at a time, onto a three-dimensional venous valve prosthetic mold. The system is able to deliver up to 100 droplets per second (each one with a volume of 2 to 60 nanoliters), and is accurate to within 25 micrometers. To ensure an even covering, the droplet feeding mechanism is mounted on a six-axis positioning system, above the mold.
Once the mold is completely covered, it is subjected to a warm stream of nitrogen. This causes the solvent to evaporate, leaving nothing but the PCU behind. The process is repeated a number of times, building up multiple layers of plastic on the mold. Once the desired thickness has been reached, the finished prosthesis is simply peeled off. By varying the amount of droplets deposited in different areas of the mold, each valve ends up with six distinct grades of elasticity and hardness - this will allow it to stand up to the stresses it will encounter within the body.
According to the researchers, the artificial valves could be implanted in the leg veins via a catheter inserted through the patient's skin. There is no word at this point on clinical trials or availability.
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