To test how important this is, prime the transducer and tubing in the same manner as for setting up a test. Keeping everything level, zero the transducer. This is much more evident in water tests than in gas tests. The most accurate test will always keep all transducers, tubing, and catheters on the same horizontal plane relative to auto zero. Connecting a tubing piece with a meniscus to another tubing piece with a meniscus assures that when the two connector ends are connected, no air enters the system.
Air rises in a fluid environment.
So when trying to de-bubble anything, make sure the highest point is the end of the flush line. For example, hold the syringe in your hand with the open tubing end higher than the transducer. Flush using a syringe. The air will naturally rise to the top. When using the Profile Plus, verify pressure response and EMG at the beginning of the Pressure-Flow study by starting the test and then immediately pressing the Pause button.