The effect of catheter to vein ratio on blood flow rates in a simulated model of peripherally inserted central venous catheters.

Background: Catheter-related thrombosis is a common complication in all anatomic sites, especially when smaller veins of the upper extremity are considered. It is presumed that the presence of a catheter within the lumen of a vein will decrease flow and potentially create stasis, and clinical data suggest that the size of the catheter impacts thrombosis rates. We sought to determine, both mathematically and experimentally, the impact of catheters on fluid flow rates.

Methods: We used fluid mechanics to calculate relative flow rates as a function of the ratio of the catheter to vein diameters. We also measured the flow rate of a blood analyte solution in an annular flow model using diameters that simulate the size of upper extremity veins and commonly used peripherally inserted central catheters (PICCs).

Results: We compared each of the derived relative flow rates to the experimentally determined ones for three cylinder sizes and found a correlation of r(2) = 0.90. We also confirmed that the decrease in fluid flow rate with each successive catheter size is statistically significant (P < .0001).

Conclusions: Our results demonstrate that fluid flow is dramatically decreased by the insertion of a centrally located obstruction. Assuming that blood flow in veins behaves in a similar manner to our models, PICCs, in particular, may substantially decrease venous flow rates by as much as 93%.