Background: Despite the growing interest in CO₂ angiography, some mechanical aspects related to CO₂ injection still need to be deepened, and some improvements are still possible. This work explores the possibility of optimizing gas injection into small-sized arteries. Since the image quality depends on how the gas fills the vessel and is strongly dependent on injection flow, the possibility of controlling the flow is mandatory to obtain good results. To better control the flow, we propose to adjunct small tubes with known hydraulic resistances in parallel to the injection catheter, allowing the generation of the desired injection flow by modulating the injection pressure. Methods: Using a mechanical mock of the cardiovascular system, we measured pressures and flows of interest and acquired the optical images of the vessel during gas injections. We performed a simulation with four different calibrated adjunct resistances in various injection pressure conditions, with and without saline flushing. Results: Our tests demonstrated that the optimized injection of the gas maintains the same procedure durations and reduces the gas volume and the local pressure increase, avoiding the local gas “explosion” in the injection site. Conclusions: Our proposal appears effective and paves the way for research into optimizing clinical CO₂ angiography procedures.