Catheters used in interventional procedures
Polyimides are used to manufacture vascular catheters for insertion into small vessels in the neck, head and brain.Guiding catheters (catheters that guides angioplasty balloons and stents) is made up of polytetrafluoroethylene (PTFE) innermost layer which is lubricant, followed by stainless steel braid wire outer layer which helps to provide support for the catheter and prevent kinking while travelling through blood vessels, and Nylon elastomer outermost layer which provides extra support for the catheter and preserve the curvature of the catheter while passing through tortuous vessels.Some catheters have a thin hydrophilic surface coating. When immersed in water this coating swells to a smooth, slippery film making the catheter safer and more comfortable to insert. Since this wire is too slippery to handle,  torque devices are used to control the direction and spin the wire. It is useful in subintimal angioplasty. However, care should be taken as it can easily cause dissection of vascular wall. Interventional procedures
Diagnostic catheters
There are various catheters used in angiography procedures. Diagnostic catheters direct wires through blood vessels. Radiocontrast agent is then injected through the catheter to visualise the vessels via various imaging methods such as computed tomography (CT), projectional radiography, and fluoroscopy. Pigtail catheter is a non-selective catheter with multiple side holes that can deliver large volumes of contrast into a blood vessel for imaging purposes. Cobra catheter is a selective catheter used to catheterise downgoing vessels in the abdomen. Cobra catheters move forward by pushing and are removed by pulling.
This is a troubling issue for many physicians, as care can be made more complicated; many patients labeled with RAD do not ultimately have asthma and most RAD patients have never formally had their airway reactivity measured.In addition to the inconsistencies of its labeling, there is also no billing designation for RAD in the International Statistical Classification of Diseases and Related Health Problems, or the ICD, which can lead to problems for healthcare facilities. Searches in the ICD, point to content relating to asthma. Some medical professionals argue that using RAD as a diagnosis will only complicate research on asthma in the context of clinical research and epidemiology. There is also dispute that by giving physicians the ability to label a patient with RAD, it gives them a fabricated sense of security that they have made a diagnosis, when no real recognizable diagnosis has been concluded. See also
Bronchiolitis

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