Arterial like waveforms ❤️Overdamped → falsely low systolic Underdamped → falsely high systolic

Added: 2026-05-07

[00:00:00]Let's talk about the different arterial line waveforms. Arterial line is only good if it works and is accurate. So let's talk about how we know if our arterial line is accurate and how we check this. First thing is we want to make sure that we level our arterial line at the flestatic axis which is the fourth intercostal space midchest aka basically your patient's armpit. This is important because if our transducer is placed too high, our blood pressure is going to read falsely low. And if our transducer is placed too low, then our blood pressure is going to read falsely high. So once the transducer is at the fleostatic axis, we're going to perform something called a square wave test.

[00:00:32]Square wave test is where you pull this little pigtail here to flush your arterial line or you can manually flush it as well. And you're going to observe for how many little oscillations there are after the square wave test. That's probably confusing. Let me break it down. So you can see here when I pull that little pigtail, that little fast flush right there. This is your square wave test. See the little square? See the little square? See the little square? When you release that little pigtail or stop flushing, you're going to observe how many little oscillations, aka I call these bounces, are after the square wave. And an optimally damped arterial line waveform, aka your arterial line waveform is accurate, you should have approximately 1.5 to two oscillations. If you have less oscillations than that, then you are overdamped. And if you have more oscillations than that, then you are under damped. Also, you should be able to see the dicrotic notch on your waveform. This is that aortic valve closing. If you cannot see it very well or it's looking a little more rounded or you're seeing additional dicrotic notches, something's up with your waveform. If you're struggling with understanding over damped versus under damped, the troubleshooting is pretty much the same. And I just did a video on troubleshooting arterial lines, so I'm not going to go into that. How I like to remember overdamped is I like to think about my hair being super wet and like you're super heavy and you're damp, right? Like it's kind of pushing it down cuz it's so heavy. And then under damped, you're not wet at all. So, it can just be whipping around. In your overdamped waveform, your systolic blood pressure is going to be underestimated.

[00:02:02]As you can see, it's not kind of going up as much. It's really like weighed down. And in an underdamped waveform that looks more whipped, your systolic blood pressure is going to be overestimated. So that's why it's really important to do your square wave test, see how many oscillations there are, make sure you are leveled at the fleostatic axis, and if you have an optimally damped waveform and your line is leveled appropriately, there's really no reason you should not trust that arterial line waveform as long as there's nothing funky going on. Okay, I hope that was helpful. Let me know if you have any more questions.