hi welcome to another MedCram lecture we're going to talk about the jugular
venous pulse specifically we're going to talk about how to measure it but it's
good for and what the diagnostic considerations are in terms of
interpreting the waveforms so if you take a look at the heart you've got the
left side and the right side this is primarily something we're going to look
at here on the right side where we put in a central line into the internal
jugular vein and down into the SVC which is usually where the tip is now this is
a hollow tube and so we're able to actually measure in a central line
what's going on in this vessel which is a extension of the right atrium now you
can also do this and we'll talk about this later you can also do something
called a right heart catheter where we actually float a right heart cath in
here into the right atrium into the right ventricle into the pulmonary
artery and we wedge the catheter here which as you recall after it goes to the
lungs we'll come back and actually measure what's going on in the left
atrium so yes we are able to actually measure what's going on the left atrium
but for right now let's just talk about the jugular venous pulse which is a
measurement that we get in the internal jugular vein the tip of which is in the
SVC so again to review there's two ways that you can look at a jvp you can
either look at the output from a central line that you've placed or number two
you can just look at the patient's jvp jugular venous pulse and that's the
internal jugular vein so that's when they're lying down you can actually look
at that area that's just around the sternocleidomastoid or the SCM and look
at the waveform as it comes up the rest of today's discussion is going to be on
specifically the central line wave output cuz that that's one way we can
actually look at the waveform and see what the waveform is doing and actually
measure the waveform so we'll talk about that before we get to that I wanted to
sort of clarify a little bit though when we should measure the central venous
pressure in a central line and that is when someone is breathing spontaneously
versus when sew-on is breathing the ventilator so this is supposed to
signify what the intrathoracic pressure is and the intrathoracic pressure also
affects the central venous pressure because the veins are running in the
thorax so when someone is breathing spontaneously this is their
intrathoracic pressure before they take a breath in and then when they take a
breath in the intrathoracic pressure goes down and then when they breathe out
it comes back up again well this is exactly what's going to happen to the
central venous pressure and so when you're looking at the waveforms it's
going to be changing and so depending on what point during the respiratory cycle
you're at you're going to get a different waveform and so the key point
here is to always measure at the end of exhalation this is the true point of
measurements the same thing goes for when you're breathing on a ventilator
except however when you're breathing on a ventilator instead of breathing in and
having a negative pressure in your chest the ventilator is pushing air into your
chest and as a result of that the intrathoracic pressure doesn't go down
but instead it goes up the same principle applies you should always
check the central venous pressure at the end of exhalation as a result of that
you'll see here indifferently that when you're measuring it on someone who is
breathing spontaneously without positive pressure ventilation that measurements
always going to be at the top of the cycle on an exhalation when someone is
breathing on a ventilator it's always going to be at the bottom but still and
exhalation so I just want to make that point for those of you who actually
measure central venous pressure I think I want to now switch to actually talking
about the actual waveforms that we see on the jugular venous waveform and the
point that I want to bring up here again is specifically we're actually we're
measuring remember the central line is going into the internal jugular vein and
it's resting just at the tip of the SVC and where the right atrium is anywhere
along this line and so think about the things that are going to make the
pressure here go up and think about the things that are gonna make the pressure
go down okay so let's think about things that would make the pressure go down and
that'll make sense later so things that are gonna make the pressure go down
it's gonna be if we have the atria the right atrium if it's relaxing if the
volume is getting bigger so atrial relaxation is gonna make the pressure go
down okay what else could make the pressure go down well if the tricuspid
valve opens and blood is allowed to leave the right atrium and go into the
right ventricle so tricuspid valve open alright what would make the pressure go
up in this area well we know that the right atrium can contract and so when it
does contract it's going to squish that blood into a smaller space that's going
to make the pressure go up so atrial contraction it's going to make it
definitely go up and also the closure of this valve so if the opening of the
valve makes it go down the closure of this valve so tricuspid closure what's
going to happen when this valve closes remember that blood is always coming
towards the heart and so as a result of that if everything is in a closed system
the pressure is always going to start to rise if this valve is closed because
this this chamber is continuously filling up with blood so with that kind
of knowledge that's actually go over what the waveform looks like so here's a
sample of what the waveform looks like at first it looks kind of complicated
but it actually is not and we've got certain waves here and you'll see that
over and over again the first wave I want to bring your attention to is the a
wave okay that's that first bump the second is the C wave okay and then we
have an X descent and then we have a V wave and then finally we have the wide
descent and it starts all over again and so this area right here corresponds
to this area right here and so this is one cycle now based on what we said
before remember where we're measuring this we're measuring this and the
superior vena cava so what is this a wave here this
a wave is simply atrial contraction and as such you're gonna see that when the
atria contract you're going to be going through starting from about right here
atrial systole this is where the right atrium is actually contracting to about
this point right here and then you've got atrial diastole okay so when the
atria when the actual muscle of the atria contract you're going to get this
upswing in pressure at that point and it's right about here
you'll get closure of the tricuspid valve this is because systole occurs
ventricular systole occurs okay we'll put that up here ern tricular systole as
a result of that when the right ventricle contracts it's going to close
the tricuspid valve now there are some people that believe that this bump right
here is the tricuspid valve actually closing some people also believe that
the C stands for carotid artery because the carotid artery runs right next to
the jugular venous pulse and that pulsation is also going to cause an
increase in the pressure that is sensed in the internal jugular vein
whichever way you like to think about it this see here is ventricular the
beginning of ventricular contraction now that the valve is closed however what
occurs is the atria continues to relax as it started here it continues to relax
down because remember we're measuring pressure on the right side and so X
specifically is atrial relaxation and that's important to remember
now that the atria has relaxed and the X wave has as we see here the X wave is
causing a descent which means that the pressure is going down in the right
atrium there's going to come a point where the blood is continuing to come in
to that right atrium and it's going to start to fill up again until it reaches
a certain point here right about the top here where the tricuspid valve opens and
as a result of that the blood then leaves the right atrium and goes into
the right ventricle and you have the by descent so what is the wide ascent is
blood from the atria going down into the ventricle so what is V V is specifically
filling of the right atrium I like to say V stands for veiling okay imagine a
German saying filling filling there is filling of the right atrium so again to
review a is atrial contraction then you have the C wave which is caused by right
ventricular contraction after that you have relaxation of the right atrium
which causes the ex descent then the tricuspid valve finally opens at the top
of the V wave so you have relaxation and then filling when the valve opens again
the pressure drops again and you have the right ventricle is now filling
during the Y wave and then finally you get back up to the top again and you're
back at another a wave so to review again a is atrial contraction see is a
ventricular contraction ex descent is atrial relaxation V is atrial filling
passively and then finally Y descent is blood going from the atria down to the
ventricle on the way back up to another atrial contraction thank you for joining
us look for the second in the series where we talk about the pathology and
how this waveform can actually help us make diagnoses