We've looked at the numbers that come
from our pulmonary artery catheter.
But now let's look
at our waveforms.
Depending on where the
tip of that catheter is,
we're going to be getting
in the right atrium,
the right ventricle,
the pulmonary artery,
and the pulmonary artery wedge pressure.
Let's take a look at each
of these individually.
And our central venous pressure,
we see that we have two
bumps in the waveform.
The first bump is our
that's when the right atrium is
contracting, you see that rise.
And then we have a
little dicrotic notch,
which is that tricuspid
valve slapping shut,
creating a little
ripple in the pressure.
And then we have a ventricular contraction,
which is our second bump, right?
Now the question I ask is,
is it the right ventricle?
Or is it the left ventricle
that creates that bump?
Well, it's not the right ventricle, because
in systole, the tricuspid valve is closed.
So that right ventricle is ascending
blood up into the pulmonary artery,
not back up into the right atrium,
so it doesn't see the right ventricle.
It actually sees the left
going through the body
back to the right side.
So that second bump is created
from the left ventricle.
The right ventricle waveform looks a
lot like the arterial line waveform,
except that it doesn't
have a dicrotic notch.
The systolic sits
between 20 and 30 mmHg,
but the diastolic
is around 0-5 mmHg.
Why is the diastolic so low?
Well, if you think about it,
it's recording the right atrium
ejecting blood into
the right ventricle.
And we know that the right atria
is the weakest part of the heart.
So really, the right ventricle is
just filled passively with blood.
So it's recording that
passive blood flow.
And our pulmonary
we see a rapid rise
when the RV contracts.
Then when the RV starts to rest,
we see a dicrotic notch,
which is the pulmonic valve closing,
and then we get
this long decline.
So it's a rapid rise
followed by a long decline,
and then you do have a dicrotic
notch in the middle of it.
Important to note that the PA diastolic
is a lot higher than the RV diastolic.
They have the same systolic because
they're both recording the RV contracting,
but the diastolic is
The pulmonary artery wedge
pressure has three bumps in it.
It looks a lot like
the CVP waveform.
It has the A wave,
the C Wave and the V wave.
We're going to look
more at the A wave,
which is what we need to get
the actual wedge pressure.
The wedge pressure is basically
the mean of the A waves.
Now that we've talked about
talked about a pulmonary artery
wedge pressure waveform
and what it looks like.
Let's talk about how do we
obtain the wedge pressure.
The syringe that comes with the pulmonary
artery catheter is a 3 cc syringe,
but it has bubbles at 1.5
cc's to prevent the syringe
from going any further back and
injecting more than 1.5 cc's of air.
If you inject more than 1.5 cc's of
air into the pulmonary artery balloon,
it could rupture it,
causing an air embolus into the lungs
or you could cause a
pulmonary artery rupture.
In order to get
a wedge pressure,
slowly inflate the syringe until
a wedge waveform is achieved.
Once that's achieved,
do not exceed 30 seconds with
the balloon being inflated.
Now when you inflate the balloon and
you don't achieve a wedge waveform,
you need to contact the physician
so they can advance the catheter
until a wedge
waveform is achieved.
When you advance the catheter
the balloon needs to be inflated.
But more importantly,
if we're withdrawing the catheter at
all the balloon has to be deflated.
What's the reason for that?
Well, you could go across the valve
with a balloon that's inflated,
you might rupture one of
the leaflets of the valves.
So it's very important that if that
physician is withdrawing the catheter
that the balloon
must be deflated.
It's important to know that the
pulmonary artery wedge pressure
has to be evaluated with an ECG
in order to find the A wave.
The A wave follows
the P wave of the ECG.
Now, why is the A wave
and the P wave of the ECG
not lined up with one another
since both are atrial contraction?
Well, it's important to remember that
the ECG is recording electricity,
which moves a lot
quicker than fluid
which is what's being recorded
by the wedge pressure.
In order to find the A waves
and the meaning of the A waves,
you need to get a full
screen of wedge waveform
and ECG and then freeze
that so that you can look at
which one is A wave and
record to get a mean.
Now let's take a look at the
progression of the waveforms
as the PA catheter is moving
through the right side of the heart.
When it gets to
the right atrium,
you're going to have your CVP
waveform which is those two bumps.
When it crosses the
then you get your bounding
right ventricle waveform.
Make note that the
diastolic is really low.
Once the tip of the catheter
passes the pulmonic valve,
that diastolic will lift up,
you'll have the same systolic
but now you've got a diastolic
and a dicrotic notch.
Then once we've advanced the catheter
even further into the pulmonary branch,
and we achieve wedge.
Now it drops down into what we
call a pulmonary wedge pressure.
And you see it looks a lot
like a central venous pressure.