Addition of polymer to radiopaque contrast material to decrease catheter flow resistance.

Abstract

RECENT SHIP-MODEL studies have shown that long-chain, high-molecular-weight polymers reduce fluid-friction drag on ship hulls (2). A similar effect was demonstrated in pipeline flows and was quickly adapted by various industries interested in reducing the cost of pumping fluids through pipelines. Recent experiments have explored the biological applicability of this phenomenon (3, 5). This report describes the use of long-chain, high-molecular-weight polymers to reduce frictional drag in high-speed injection catheters. Previous work in this laboratory (1) has shown that catheters used clinically in high-speed injections generally operate in a turbulent flow condition. Reynolds numbers in the range of 6,000–15,000 are found in catheters under these conditions. The application of classical engineering hydrodynamics is useful in the description of pressure-flow characteristics of injection catheters (1). The addition of high-molecular-weight polymers reduces frictional drag only in turbulent flow conditions. However, White and Hoyt (5) have found that fluids to which polymers have been added maintain a laminar flow even though the calculated Reynolds number is 4,000–5,000. Methods In order to measure drag reduction, a system was devised which enabled us to measure flows and pressures accurately during injection through a steel catheter of fixed length and diameter. Using this type of catheter eliminates not only the problems of expansion in polyethylene catheters but also the flow variation due to whipping or motion of the catheter during the injection. In these experiments, an injector driven by gas at a constant pressure was used. This injector produces a square pulse of pressure and flow with no over-shoot or undershoot. Pressure was measured at the injection nozzle with a Statham Model PG769 high-pressure transducer with ranges of 0–1,000 psi. This transducer was mounted in a specially built chamber which could be connected to the output nozzle of any injector system and provided a precise measurement of pressure at the proximal end of the catheter. Flow was calculated by measuring the volume injected over a fixed period of time. The injector was electronically controlled and injection time was set at 1.0 ± 0.01 second. The catheter used in this study was constructed from stainless-steel hypodermic tubing 50 em long and 0.16 em in diameter. Injections were made at room temperature with water and a number of contrast materials. After the normal pressure-flow relationship was established for each contrast medium through the catheter and injection system, poly-ethylene oxide (Polyox) 3 in quantities of 30 parts per million (ppm) was added to the solutions of the various contrast materials and the water.