Chest X-Ray Interpretation Explained Clearly – How to read a CXR

October 12, 2019

Welcome to another MedCram
lecture we’re going to talk about chest x-rays today how to interpret them how
to review them in a systematic way and make sure that you get the
interpretation correct the first thing that we’ve got a review is how to
interpret a chest x-ray so an x-ray is simply a film that is looking at
material hitting the film and causing it to either be dark or white it’s a black
and white film and that correlates to about five different areas of density
okay so everything’s black and white going from black this represents
basically air so things that are air density on the
chest x-ray are going to appear black things that are dark gray is going to look like subcutaneous
tissue or fat 3 you’ll kind of see light gray and that’s usually soft tissues
like the heart blood vessels things of that nature it’s a soft tissue for is
going to be just off-white and this is going to be bone so ribs clavicle things
of that nature and then finally you’re going to see bright white and so this is
things like metal which is sometimes seen on chest x-rays either because of
pacemakers defibrillators or even buckshot from gunshot wounds so these
are your five things that you’re generally going to see now because of
these different densities you’re going to notice things on the chest x-ray if
there is a difference in density by objects that are next to each other
for instance if we’ve got object a sitting next to object B the only way
you’re going to be able to see this line that separates them is if the density of
B is of one of these five different densities and it is different than the
density of a let’s give an example of this here you’ve got the hemidiaphragm
at the sits at the bottom of the lungs that hemidiaphragm is made out of muscle
and right below it sits the liver both of which would be soft tissue and would
be light gray okay so that soft tissue density well right above that is the
lung and the lung is air density and so because you have two objects right next
to each other with different densities on this list you’re going to actually see that line
very well now if something were to happen in that lung let’s say there were
an ammonia that pneumonia in that area is going to
turn this air dense lung into a water dense lung and so therefore this
demarcating line is going to disappear and you’re not going to see it on the
x-ray and so if you lose that line you can say then that there is no
demarcation there between the different densities so you would call that a right
lower lobe pneumonia that’s as an example now there are many ways of going
through this in a systematic way one that was proposed by Talley and O’Connor
at the Trinity School of Medicine in Dublin Ireland that’s just one of many
examples but let’s go through a normal chest x-ray and kind of go through the
ABCs of how this works okay but before I do that let me just go through a couple
of basics so if you’ve got a person standing which is usually the best way
of doing a chest x-ray there’s two ways of doing it you can either shoot the
film from front to back which is known as an AP or from back to
front which is known as a PA posterior-anterior versus anterior
posterior and it’s really all about where you put the board the board that’s
collecting the x-rays if the board is behind the patient like this
that’s called an AP that’s typically what you don’t do in a portable x-ray
when the patient is in the intensive care unit when the patient’s ambulatory
the board is going to go in front now the reason why it’s better to have it in
front is that the heart and those objects are going to be closest to the
film and that way you’re going to get less artificial increase in size you
know that when you’re playing hand puppets or puppet fingers with shadows
against the wall that the farther you move away from the wall the bigger your
hand shadow is going to be and it’s the same way with x-rays the closer you are
to that plate the more truer and better focused you’re going to be on getting
the actual true size of that object so in generally speaking a PA
film is probably the best now with a PA film they usually do something called a
lateral film as well basically a side view and so that way on an x-ray you’re
only going to see two dimension on a lateral film you’ll be able to actually
make out three dimensions and you’ll be able to see things behind the heart for
instance we’ll just pair it as though it’s in the middle of the heart on a
lateral film you’ll actually be able to see it behind the heart and be able to
localize better where that object is so generally speaking in a hospital when a
patient is sick laying in a bed you’re just going to get one view an AP view
which is susceptible to magnification of the heart and the vessels in an
outpatient setting where the patient’s ambulatory you’re going to get a to view
PA and lateral what you’re not going to get magnification artificially and
you’re going to be able to get a better view now generally speaking we’d like to
have patients take a deep breath in when they shoot the film that way we can
accentuate and see very well all the different areas of the lungs however
there’s a couple of situations that you should know where you want to do a
exhalation film and that is when you’re trying to look for a pneumothorax and
the reason for that is that’s what it’s going to make the pneumothorax or the
pleural air to be greatest and most accentuated okay the other reason why
you might want to do that is if there is a delectable more specifically because
that air trapping is going to be accentuated on exhalation because all of
the air is out of the lung except for that area where air is not able to come
out so these are the two areas where I would do a film on exhalation rather
than inhalation well that being said when you approach a chest x-ray the
thing that you really want to make sure is that you’re looking at the right
x-ray nothing is worse it’s going through the whole process of looking at
an x-ray only to realize that a it’s either the wrong patient or B it’s from
the wrong date and once you’ve got that then you can move on to the systemic
review okay so here is an x-ray for review notice that this little
marker up here which says L on it is referring to the side of the patient
remember that the right side of the screen is always the left side of the
patient and vice-versa so the first thing that I like to do is I like to do
a first a is the trachea I like to look for the trachea as you can see it comes
down in this area right here okay and then notice that it branches this way
and if you can make it out you can see it branches this way and down like this now looking at the trach it is important
because you can tell if it’s being shifted in one direction or the other if
it’s being shifted in one direction or the other that could mean the presence
of a pleural effusion or atelectasis pulling or pushing the trachea in one
direction or the other the other thing too is if the patient is
intubated I can see if the endotracheal tube is in that trachea as well and we
typically want that between three to five centimeters away from the Carina
which is right there so one example of this for instance if we had a lot of
fluid on this side either inside or outside the lung let’s say we had
whiting out on one side of the lung the question is is that a pleural effusion
or is that a complete and electus as’ of the right lung and the way you be able
to tell is if this was a pleural effusion a pleural effusion pushes and
so the trachea would be deviated to the opposite side however if it was an
elective atelectasis is a collapsible lung it would pull it towards the right
side of the patient or the left side of the screen the next thing I like to look
at is B or bone so I’d like to look at and compare the bony structures paying
very close attention to site size shape shadows and borders
you’ve got the clavicles right here okay so you can look for any kind of
fractures you’ll notice here there’s like a cacophony of ribs going by the
ones that are very horizontal are the posterior aspect of the ribs and then
you’ll see ones in the front that are coming down these are the anterior
portion so you can see if those are fractured or not this one right up here
at the top you can see here right above the clavicle is related to the first rib
you see the second ribs here as well you can also look at the spinous processes
and see if they are lined up all the way down and you can look along the edge and
see if there’s any compression fractures so these regular intervals will be
disturbed if there’s any compression fracture so you can look at those as
well the other thing you can look at is for
lytic lesions in the bone I don’t see any here this is a normal x-ray but
sometimes you can find lytic lesions and these are look like basically holes in
the bone they’re lytic lesions so they have air density inside of bone density
sometimes you can find some extra cervical ribs which a little bit off of
this but you wouldn’t be able to see that here so that’s B for bone so we’ve
covered a and B join us for the next video where we talk about cardiac which
is C thanks for joining us you

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