Multifunctional testing of PTCA balloon catheters]

New in vitro measuring methods for balloon catheters used for percutaneous transluminal coronary angioplasty (PTCA) and their verification in a complex test device are presented. This system can mimic all relevant application situations. The central element of the test device is a coronary vessel model matching the physiological situation in terms of geometrical structure and frictional properties. Reactive force sensors are used to measure the application-relevant forces exerted by the catheter on the model vessel walls and accessories, such as guide wire and guiding catheter. To generate a kink-free advancement of the catheter and permit measurement of the active forces, an alternating drive unit has been specially developed. The testing and application of the newly developed methods revealed statistically significant differences between various types of catheter. The test device closes a gap between complex but subjective clinical tests, and individual objective, but application-removed in vitro test setups for PTCA catheters. While the initial prototype had shortcomings with regard to the reproducibility of measurements, successor systems developed for industrial use are now in production. The properties of these measuring systems developed for the benefit of manufacturer and reprocessor of PTCA catheters are discussed.     

Designing and testing scene enhancement algorithms for patients with retina degenerative disorders

Background  

Retina degenerative disorders represent the primary cause of blindness in UK and in the developed world. In particular, Age Related Macular Degeneration (AMD) and Retina Pigmentosa (RP) diseases are of interest to this study. We have therefore created new image processing algorithms for enhancing the visual scenes for them.     

Haemocompatibility of coronary catheters.

BACKGROUND: Unwanted side-effects like thrombotic-thromboembolic processes accompany the intravascular use of catheters. The influence of the physico-chemical properties of the catheter materials on these processes is not completely understood. METHODS: The haemocompatibility of angiography-catheters (n = 10) (Super Torque Plus, CORDIS, Johnson & Johnson company) was examined in a perfusion-model filled with platelet-rich plasma and either compared to a non-thrombogenic (silicon-tube) or to a thrombogenic surface (glass). As test-parameters the number of single circulating thrombocytes, of circulating platelet-aggregates, of circulating activated thrombocytes (CD62) and the thrombin generation (thrombin antithrombin III-complexes) were evaluated. RESULTS: None of the test-parameters showed differences between the non-thrombogenic control-system and the angiography-catheters. Both systems, however, differed significantly and relevantly from the system filled with the glass-beads (the thrombogenic control-systems). CONCLUSION: With respect to the platelet reactivity angiography-catheters of the examined type can therefore be regarded as non-thrombogenic or haemocompatible.     

Cardiac tamponade and central venous catheters.

An analysis of the reports on 16 patients who developed cardiac tamponade, complicating the use of central venous catheters, showed that 14 died. The two survivors were treated by removal of the catheter and needle aspiration of the pericardial fluid. Some patients complained of warning symptoms such as nausea, pain, and dyspnoea, and the combination of tachycardia, hypotension, and raised venous pressure was common. We suggest that awareness of the hazard, radiographic visualization of the catheter tip, and expeditious treatment would reduce the mortality.     

Customized vascular catheters for rodents

Custom arterial and venous catheters were made for rodents from polyurethane tubing. The low thrombogenicity and toxicity index, chemical stability and resiliency of polyurethane made this tubing an ideal catheter material. The tubing is shaped using peanut oil heated to 160 degrees C. Sealing these catheters is accomplished simply by heating the tube end with a hot object and pinching it between the fingers. Chronic catheter patency was maintained using Burr's solution (9:1 mixture of glycerine and heparin). No flushing was necessary.     

Management of obstructed balloon catheters.

Failure of a balloon catheter to deflate is not uncommon and prevents its removal. Methods of overcoming the problem include traction, bursting the balloon by overinflation, dissolving it with solvents, puncturing it percutaneously with a needle, or puncturing it with a wire stylet passed through the catheter. All except the last technique have major disadvantages and are of questionable safety. Transcatheter puncture of the balloon was used in 16 patients to remove obstructed balloon catheters without any technical difficulty, distress to the patient, or complication. The procedure is safe, simple, and does not require an anaesthetic. If necessary it could be performed safely by nursing or paramedical staff without the patient having to be admitted to hospital. It is the method of choice for the management of this problem.     

Urethral response to latex and Silastic catheters.

The reaction of the urethral mucosa to latex and Silastic catheters was compared in two groups of patients undergoing prostatectomy. The bacteriologic response in the two groups differed little; however, Silastic catheters produced less cellular reaction than latex catheters.