A syringe concentration describes what was prepared. Measurements at the far end of the tubing can answer a different question. A laboratory study by Maiguy-Foinard and colleagues tested this distinction using eight commercially available double-lumen extension sets.
The researchers infused diazepam through sets made with different plastics and sampled the fluid at the outlet. At 150 minutes, the mean outlet concentration ranged from 48.58% of the starting syringe concentration for one polyurethane set to 85.06% for a polyethylene/polyvinyl chloride set. The team also tested isosorbide dinitrate and ran norepinephrine controls. Performance varied among extension sets, including sets with the same general material designation.
Those percentages compare concentrations at one time point. To calculate the amount delivered over the full infusion, a reviewer would need the flow and concentration over time. Applying either percentage directly to a charted syringe dose would confuse a point measurement with a cumulative amount.
The experiment isolates drug loss associated with the tested devices under laboratory conditions. A case-specific reconstruction needs the tubing reference, drug formulation, concentration, flow, priming and infusion timeline. A generic description such as “double lumen” leaves out the device-level differences measured in the study.