Peripheral venoarterial extracorporeal membrane oxygenation (VA-ECMO) and minimally invasive cardiac surgery often require femoral arterial cannulation, wherein lower limb ischemia remains a major complication. Although introducer sheaths with side ports are widely used to provide antegrade limb perfusion, their pressure–flow conducted using an extracorporeal membrane oxygenation circuit to compare the flow performance and pressure loss of two introducer sheaths with side ports and a catheter without a side port. Flow was measured at inlet pressures of 50–300 mm Hg, and pressure loss across the side port region was directly evaluated. In sheaths with side ports, increasing perfusion pressure produced progressively attenuated flow augmentation and an early plateau, whereas the catheter without a side port showed a linear pressure–flow relationship without saturation. In the 5Fr sheath, approximately 70% of the total pressure loss originated from the side port region, regardless of the perfusion pressure. The measured flow strongly correlated with flow meter values (r = 0.9997). These results indicate that the side port structure is the dominant resistance element and may explain why distal perfusion catheters fail to resolve limb ischemia. Catheters without side ports may help when conventional devices provide insufficient antegrade perfusion.