To evaluate the effect of catheter connections on drainage catheters’ flow rate.

The in vitro model used commercially available catheters (8.5-F, 10.2-F, 12-F, and 14-F), connections - Luer-lok (2.33mm inner diameter), and stopcocks (1.33mm, 2.00mm, and 2.67mm inner diameters), water, ultrasound gel, textured vegetable protein (TVP) 2-mm particles, and collection bags. Plain water, viscous fluid (30% ultrasound gel solution in water), or water/viscous fluid with TVP were placed in collection bags and drained by gravity through each of the catheters and each connection. The flow rate was measured, recorded, and compared for each catheter and each connection as well as to the control flow rate of the catheters without connections. Ten one-minute trials were performed, and the mean flow rates were analyzed using Student t-test and Pearson correlation coefficient.

Flow rate was significantly decreased in the 12-F and 14-F catheters with all stopcock and Luer-Lok connections with both water and viscous fluids. There was no significant reduction in flow for the 8.5-F and 10.2-F catheters with the 2.00-mm, 2.33-mm, and 2.67-mm connections; flow rate was significantly decreased in the 8.5-F and 10.2-F catheters with the 1.33-mm connection. A majority of trials with particulate fluid became occluded, and no consistent pattern between connections could be made.

This in vitro study suggests that stopcock and Luer-Lok connections limit catheter flow rate when their inner diameter is less than that of the drainage catheter.