An arterial line simulator with a notch that isn't drawn in
The Patient Simulator builds the arterial pressure trace from a forward pressure wave and a reflected one, so the dicrotic notch is a real product of that reflection, not a shape stamped onto every beat.
A notch that comes from physics, not a template
The trace is the sum of a forward systolic wave moving out from the heart and a reflected diastolic wave coming back from the periphery. The dicrotic notch sits exactly where those two waves interact, plus a distinct narrow negative incisura marking the moment the aortic valve closes. Neither is hand-drawn onto the waveform; both come out of the same wave math that produces the rest of the beat.
Diastole shortens the way it actually does
As heart rate climbs, the diastolic portion of the beat compresses with the square root of the cycle length, the same relationship the QT interval follows, rather than shrinking in a straight line. A linear compression made the dicrotic notch vanish by a heart rate of about 100, which isn't how a real arterial trace behaves even in a fast patient.
The scale adapts to the patient, not a fixed range
Rather than a wide fixed mmHg axis that makes a normal 120/80 look nearly flat, the display auto-ranges to the current systolic and diastolic values with some headroom, so a normal trace fills the box the way it does on a real monitor and an abnormal one is still readable. MAP is calculated from the same numbers and shown on its own line beneath the systolic/diastolic pair.
No pulse, no trace
In pulseless rhythms (VF, asystole, PEA) the arterial line correctly goes blank rather than continuing to draw a plausible-looking pressure, since there's no real pulse pressure behind it to display.
Why the cuff and the arterial line rarely show exactly the same number is explained in NBP vs ABP.
What the dicrotic notch itself tells you, and why it can vanish, is covered in the dicrotic notch.
Frequently asked questions
How do I set the blood pressure?
With the ABP slider on the controller. The minus and plus buttons step 5 mmHg at a time, and the diastolic pressure follows the systolic automatically. The same slider sets what the NBP cuff reads, which is why the controller labels it ABP (NBP).
Where is the MAP shown?
On its own line under the systolic/diastolic pair, calculated from those two numbers, the way most bedside monitors show it.
What happens to the arterial line in cardiac arrest?
In every pulseless rhythm the pressure number is blanked and the arterial trace goes flat, even if the ECG still shows organised complexes, as in PEA.
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