Technology and clinical application of large-bore and implantable catheters

The K-port concept: Proposal for optimising a fully implantable port system

Objective. Typical reasons for the malfunction of implantable central venous catheters involve obstructions caused by blood clots, perforation through the skin, and contamination of the device. The objective of introducing this new port concept is to reduce the incidence of complications by making alterations to the design.

Design. The main characteristics of this new port chamber are its drop-shaped interior, which opens into the catheter-connecting piece rather like a funnel, the lateral position of the puncture membrane, and the exchangeable catheter connection device. As a result, the following improvements with regard to conventional port catheters are feasible.

Results. The puncture is made laterally next to the port chamber in a large, previously unstressed area of skin. The subcutaneous puncture channel can be used for a greater length of time so as to avoid ascending infections. In the event of an occlusion of the catheter, a wire can be pushed through the cannula to clean it. The puncture cannula lies against the skin and can be attached more readily. Various port chamber sizes can be combined with different catheter thicknesses to best meet the individual requirements of the patient.

Current Status. The afore-mentioned port system is still at a conceptional stage of development. There are no data on practical experiences with the K-port, as licensing details have yet to be agreed upon with a manufacturer. We have applied for a patent for this device.

Pressure Drop Through Generic Lumens of Hemodialysis Catheters

A unique, air-based system has been developed and implemented for rapid and accurate determination of pressure drop versus flow rate characteristics of generic catheter lumens; dimensionless scaling parameters can be effectively used to express these characteristics in units of blood flow used in the clinical setting. Theoretical models are compared with experimental data. For flow and geometric parameters of practical importance, the pronounced effect of developing flow in the lumen must be accounted for in calculation of the pressure drop along the lumen. That is, the theory of classical Poiseuille flow substantially underpredicts the pressure drop. Moreover, a side hole can induce significant, and in some cases large, values of pressure drop, even when the area of the hole exceeds the cross-sectional area of the lumen.