Pressure monitoring on pediatric Extracorporeal Membrane Oxygenation (ECMO) circuits is used to aid in the evaluation of patient hemodynamics and circuit health. Extracorporeal Life Support Organization (ELSO) recommends monitoring pressures on the venous line, pre-, and post-oxygenator. In order to keep pressure ports patent, crystalloid can be used as a flush. The fluid transfused to the patient through these lines can be challenging to quantify accurately due to variance in clinician practice. Currently, there is no published data or practice suggestions on this topic. In Vitro experiments using Edwards True Wave transducers and pressure bags were constructed, allowing for common negative and positive pressures to be simulated. Passive volume infused through the transducer as well as intermittent active flushing by pulling the snap tab were measured and the volumes were recorded. When the pressure transducer and associated tubing are kept patent by using a pressurized IV bag, per the instructions for use, the daily volume transfused was found to be 319.6 mL or close to a typical neonate’s total blood volume. Rather than using passive or active flushing, the use of automated syringe pumps can reduce the transfused volume to 24 mL per day. Further study is recommended to develop and publish best practices.