Tube stent

C., Schmohl, K., Martin, D.P., Ydlliams, S.E., Sternberg, K., and Schmitz, K.P. (2007) A biodegradable slotted tube stent based on poly(l-lactide) and poly(4-hydroxybutyrate) for rapid... 

Dumon (Dumon 1990) introduced another silicone tube stent, which is available in different lengths and diameters and comes with external protrusions for better fixation. The Dumon stent (Novatech, Aub-agne, France) has become the most commonly used silicone stent. This stent requires a rigid bronchoscope and a special introducer system for placement. Because so much clinical experience (Cavaliere et al. 1996 Dumon et al. 1996) has been gained with this stent it has become the gold standard for most bronchoscopists. Therefore, newer stent designs must be measured in comparison to this stent. 

This chapter focuses on the insertion technique for metallic covered and uncovered stents. For placement of plastic tube stents (like the Montgomery, Dumon, or Dynamic Stent) special introductory systems and rigid bronchoscopy are required. These stents are usually placed by experienced interventional bron-choscopists. The interested reader might refer to one of the review articles on interventional bronchoscopy (SoNETT et al. 1995 Beamis and Mathur 1999 Mehta and Dasgupta 1999 Wood 2001). 

One of the potential advantages of metal stents over the plastic tube stents is the possibility of placement under conscious sedation by flexible endoscopy or fluoroscopy only. However, for a safe and durable access to the tracheobronchial system, the possibility for fine adjustments of the inserted stents, additional therapeutic measures, and permanent control of ventilation, most interventionists prefer to carry out stent implantations under general anesthesia and with the use of a rigid ventilating bronchoscope. Such a setting enables high frequency Venturi jet ventilation. 

The focus of this chapter is primarily on metallic stents. For a detailed overview of the results of placement of plastic tube stents for tracheobronchial obstructions due to malignant tumors, the interested reader is referred to one of the review articles on stenting of the tracheobronchial system written by experienced interventional bronchoscopists (thoracic endoscopist) (Colt and Dumon 1995 Mehta and Dasgupta 1999 Rafanan and Mehta 2000 Wood 2001). 

Rarer complications of plastic tube stents include tracheobronchial ulceration with secondary hemorrhage, perforation of the tracheobronchial wall with secondary mediastinitis and septic shock, tumor overgrowth at the proximal or distal stent margin. 

Interaction of the metalhc stent and the tracheobronchial wall is expected unlike plastic tube stents. This leads to specific problems. Removal of a metalhc stent, which is incorporated into the mucosa several weeks after deployment is extremely difficult and sometimes requires laser destruction of the stent struts in order to remove the stent piece by piece . Similarly, repositioning of an embedded metal stent is more difficult than relocation of a silicone stent. Covered metal stents exert less problems regarding removal and repositioning than uncovered mesh stents, where the open mesh design can lead to complete inoculation of the small stent wires into the mucosa. 

Covered Wallstents have a complication profile similar to plastic tube stents. Bolliger et al. (1996) found retained secretions in five out of 27 patients, granuloma formations at the stent ends in four, and stent migration in four. 

Grabow, N., Btinger, C.M., Schultze, C., et al. A biodegradable slotted tube stent based on poly(L-lactide) and poly(4-hydioxybutyrate) for rapid balloon-expansion. Ann. Biomed. Eng. 35, 2031-2038 (2007). doi 10.1007/sl0439-007-9376-9... 

Stenting Placement of a stent (a short metal or plastic tube) to allow blood flow through an artery. 

Angioplasty may take between 30 minutes to 3 hours to complete. It begins with a distinctive dye that is injected into the bloodstream. A thin catheter is then inserted into the femoral artery of the leg, near the groin. The doctor monitors the path of the dye using x-rays. He moves the tube through the heart and into the plaque-filled artery. He inflates the balloon, creating more space, deflates the balloon, and removes the tube. It is important to note that the plaque has not been removed it has just been compressed against the sides of the artery. Sometimes, a stent may be implanted, a tiny tube of stainless steel that is expandable when necessary. Its function is to keep the artery open. 

Siloxane-containing devices have also been used as contact lenses, tracheostomy vents, tracheal stents, antireflux cuffs, extracorporeal dialysis, ureteral stents, tibial cups, synovial fluids, toe joints, testes penile prosthesis, gluteal pads, hip implants, pacemakers, intra-aortic balloon pumps, heart valves, eustachian tubes, wrist joints, ear frames, finger joints, and in the construction of brain membranes. Almost all the siloxane polymers are based on various polydimethylsiloxanes. 

A vascular stent was coated with the step 1 product and then placed in a 13 mm x 100 mm glass test tube and treated with 10 ml 3% sodium methoxide in methanol. 

It was then placed into a 250-ml Parr reactor and then pressurized/depressurized 10 times with nitrogen at 10 atmospheres. The reactor was then treated with two pressur-ization/depressurizations with nitric oxide at 30 atmospheres. Finally, the vessel was filled with nitric oxide at 30 atmospheres and left at ambient temperature for 24 hours. The vessel was then repeatedly pressurized/depressurized with nitrogen gas at 10 atmospheres. The test tube was removed from the vessel and sodium methoxide solution decanted. The stent was then washed with 10 ml of methanol and three times with 10 ml diethyl ether and then dried under a stream of nitrogen gas and the diazeniumdiolated stent isolatedt. 

Figure 10.13 shows examples of high-resolution patterns formed on small scale cylindrical objects - optical fiber and microcapillary tubes [1]. These simple devices (integrated photomasks for optical fiber Bragg gratings and intravascular stents), require only one patterned layer. 

Contrast medium is injected into the bile ducts via an endoscopic tube. X-rays are then used to visualise the pancreas and biliary tree. Gallstones can be removed during ERCP and stents can be inserted to widen narrowed bile ducts, which may be the cause of jaundice. 

In some patients, a stone may be able to be seen only after a narrow tube called a stent is placed in the ureter. The patient is first put under anesthesia. Then the... 

Before insertion, the stents are crushed down so they can be fed into the artery through a thin tube. As the crushed stent heats up in the blood it returns to its original shape. 

As the majority of patients are still not suitable for radical treatments due to age, physiologic status, or advanced disease, good palliation with minimal morbidity and mortality is important. Patients suffering dysphagia may benefit from intubation of strictures with insertion of rigid plastic tubes or self-expanding stents. Simple dilation offers short-term relief but does have significant risk of perforation. Some patients may benefit from chemotherapy or radiation therapy. 

Careful correlation with prior CT images will help plan the puncture in relation to the markers on the stent graft. Ideally the left side access is used to avoid IVC. However, if necessary the puncture can be done through the IVC. When performed under fluoroscopic guidance it is useful to frequently rotate the X-ray tube from the AP to the lateral projection, and in between, to help in assessing the needle track, and to avoid puncturing the stentgraft. 

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