Papers by Keyword: Catheter

Abstract: The purpose of this research is to investigate the mechanical property of catheter, which is made of soft nylon resin and is reinforced with thin stainless wires called braid. In this paper, the relation between the deformation speed and the buckling phenomenon is examined by using the catheters which have a viscoelastic property. If we image the actual usage, the different types of several loads such as torsion and bending are applied simultaneously to the catheter. Thus, it is expected that the buckling phenomenon of the catheter will be more complicated. In this study, as the initial step to reveal the buckling behavior under combined loading state, the buckling tests under combined loading of compression and torsion are carried out under the proportional deformation path by changing the speed of axial displacement and the torsional angle. And then, the effect of the stress relaxation on the occurrence region of buckling under combined loading state is revealed in this paper.

Abstract: The purpose of this research is to investigate the relation between the deformation speed and the buckling phenomenon of the catheters, which is made of soft nylon resin and is reinforced with thin stainless wires called braid. In general, the buckling phenomenon of the catheter is complicated because the different types of several loads such as torsion and bending are applied simultaneously to the catheter. In this study, as the initial step to reveal the buckling behavior under combined loading state, the buckling behaviors under combined loading of compression and torsion are examined. Especially, in this study, the buckling tests under various initial torsion are conducted by changing the axial displacement speed. And then, the effect of the stress relaxation on the occurrence region of buckling under combined loading state is revealed in this paper.

Abstract: This paper describes the creep deformation behavior of catheter which is made of soft nylon resin and is reinforced with thin stainless wires called braid. In this research, the creep deformation behavior of uniaxial tension generated under two-stage step stress is examined as the most fundamental case that the principal axis of stress is fixed in a space. And the mechanical model, which is composed of a Voigt unit and a single spring element, is proposed for representing the creep deformation behavior. Then, the numerical simulation is carried out, and the validity of this model is verified by comparing the analytical results with the experimental results under two-stage step stress.

Abstract: The purpose of this research is to examine the physical property of the catheter, which made of soft nylon resin and is reinforced with thin stainless wires called braid. The effect of braid on the mechanical property of the catheter is revealed by investigating the relationship of the stress relaxation and the relative angle between the braid and the principal axis of stress under combined loading of bending and torsion. Inthe first place, in order to investigate the phenomenon of stress relaxation under combined loading, the experiments under single stage step strain have been carried out by changing the ratio of bending and torsion, and the relation between the coefficient of viscosity and the relative angle of the braid is revealed. In the second place, the experiment under two-stage step strain are conducted by changing the order of bending and torsion, and the effect of these loading histories on the visco-elastic properties is examined. Moreover, the numerical simulation under two-stage step strain is carried out by using the estimated coefficient of viscosity, and in this paper, the validity of this analytical model is confirmed by comparing with the experimental results.

Abstract: Generally, as for the material of catheter, a soft characteristic is necessary so as not to damage vascular wall etc. On the other hand, responsivity and enough rigidity are required for the surgical operations such as myocardial infarction or cerebral infarction. Therefore, the catheter, which is made of soft nylon resin and is reinforced with thin stainless wires so called “braid”, is chosen as the subject of this study. The purpose of this study is to reveal the effect of braid on the mechanical property of the catheter by investigating the relationship of the stress relaxation and the relative angle between the braid and the principal axis of stress. Especially, in order to investigate the stress relaxation under combined loading, the experiments of two-stage step strain for tension and torsion are carried out with different deformation paths. Consequentially, the phenomenon of the stress relaxation reduces with the relative angle becomes smaller. Moreover, the numerical model under two-stage step strain is proposed in this paper, and the validity of this model is confirmed by comparing the calculated results with the experimental results.

Abstract: Nitric oxide (NO) produced in the endothelial cells and other tissues has been known to play a range of physiological roles including vasodilation. Thus, direct in vivo measurement of NO is of great importance for clarification of physiological roles of NO and development of therapeutics using NO. It has long been assumed that NO is readily oxidized in blood and cannot be detected; however, some recent reports demonstrated much longer half-life of NO in the blood stream in vivo. Recently, we reported the basic performance of an NO sensor which is applicable to in vivo measurement. This sensor can detect NO in the blood stream in an anesthetized rat and some biological samples including a dialysis solution. In these studies we found that NO itself showed dynamic changes different from these of oxidative products of NO (nitrite and nitrate) that are conventionally used as indices of NO level. We have also developed a catheter-type NO sensor and demonstrated validity of the sensor for in vivo measurement of NO in the aorta and coronary sinus of anesthetized dogs and rabbits. Both endothelium-dependent and -independent NO productions could be detected. In conclusion, the NO sensor and the catheter-type NO sensor are applicable to direct measurement of NO in biological samples even in vivo and will contribute to clarification of physiological roles of NO.