It’s a very specific sign that can only be adequately recognized when monitoring pressure with an arterial catheter.
Pulsus paradoxus is asignof some other condition and by itself is not a medical condition.
When youbreathein (called inspiration or inhalation), your blood pressure drops a little.
Verywell / Jessica Olah
How much of a drop is too much?
This is the normal way that humans take a breath.
It’s called negative pressure ventilation and it can be compared to the bulb of a turkey baster.
When you let go of the baster, the bulb expands and air rushes in.
The whole thing works in reverse as well.
That works with the turkey baster as well.
Fluid and Air Dynamics
Not only is air affected by pressure, but so is fluid.
That’s why the turkey baster has a bulb and why it’s called a turkey baster.
This is one example of using pressurein this case, to baste.
The difference is that blood is coming from the rest of the body rather than from outside like air.
The thorax is a cavity inside the body that is isolated from the other cavities.
So when it sucks, it pulls in air and fluid.
Even the heart itself works this way.
Blood is moved through the process as the heart expands and contracts.
The expansion of the chest in between compressions encourages critical blood return from the brain and abdomen.
Imagine if you were walking up an escalator and someone kept flipping the switch between up and down.
Your progress up the escalator is like blood flowing through the arteries.
Each step is a little push just like systole pushes blood.
Each time the escalator is going up, it’s like exhaling and pushing you a little farther up.
There is a very rare situation of reverse pulsus paradoxus that can occur during right ventricular congestive heart failure.
(More on that below.)
An arterial line is a catheter inserted into an artery.
One of the reasons to regularly measure blood pressure at consistent intervals is to identify trends.
A typical question caregivers get from both patients and newer care providers is why the blood pressure will fluctuate.
It is a dynamic, organic process that has many factors affecting it.
There is probably a clue in the types of conditions that cause pulsus paradoxus.
They all have to do with extra pressure being exerted on the heart.
The following is a list of medical conditions that can cause pulsus paradoxus.
The pericardium is very tough and unforgiving.
When blood seeps into it, the pericardium doesn’t stretch much.
The heart gets squeezed by the lack of space left over as blood collects.
This condition is known ascardiac tamponade, or sometimes as pericardial tamponade.
In many cases, the leak is self-limiting.
One hallmark of the tension pneumothorax is a significant and consistent drop in blood pressure.
Pulsus paradoxus is an earlier sign that occurs as the tension pneumothorax is developing.
Pericarditis
Besides cardiac tamponade, the pericardium can also cause problems if it becomes infected or inflamed.
This blood vessel traffic jam is known ascongestive heart failure (CHF).
Or, it could be seen as similar to the effect of positive pressure ventilation as described.
All we know so far is that it has to do with pressure in the thoracic cavity.
Indeed, pressure is what keeps blood going round and round, and air going in and out.
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