Four catheters (Ash Split Cath, Tesio, Duo-Split, and Duo--Flow; Medcomp, Harleysville, PA, U.S.A.) were tested in a temperature-controlled in vitro setup filled with 50% aqueous glycerin solution to determine hydraulic resistance at different flow rates. All these catheters have side holes; hydraulic resistance was determined with these holes open and closed. Due to extra pressure losses near the catheter tip, the pressure-flow relationship deviates from Poiseuillian theory and is generally quadratic in nature. An equivalent diameter was derived from the data. This equivalent diameter can be used to evaluate performance using a single number. Permanent catheters can easily deliver 300 mL/minute under optimal circumstances, but acute catheters are, in practice, limited to 200 mL/minute, and even somewhat less in the coaxial Duo-Flow type. Permanent catheters have larger equivalent internal diameters (1.8 vs 1.45 mm). Covering the side holes does not influence hydraulic resistance to a great degree, except in the arterial limb of acute catheters. These results indicate that, especially in acute catheters, obstruction of the side holes or fibrin sleeve/thrombus formation over the inlet holes may severely impact the available blood flow rate during dialysis. On the other hand, side holes in permanent catheters or venous limbs seem to be superfluous for performance reasons.

No abstract

“Rail Baltica” project is priority project No 27 “Rail Baltica” axis Warsaw-Kaunas-Riga-Tallinn-Helsinki, approved by Decision No 884/2004/EC of the European Parliament and of the Council of 29 April 2004 amending Decision No 1692/96/EC on Community guidelines for the development of the trans-European transport network (European Union, 2004). An article analyzes the changes in the main parameters of the 1435 mm gauge railway infrastructure during the whole period of the “Rail Baltica” project, determines their impact on the project implementation time-line, purposes and results, highlights basic parameters which need to be met during modernization. On this basis, the main criteria for the evaluation of Rail Baltica rail infrastructure were selected. An expert survey was conducted to evaluate the criteria. The Kendall method was used to calculate the criteria weights. The article ends with a scientific discussion.