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 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 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 that's usually
subcutaneous tissue or fat three you'll kind of see light gray and that's
usually soft tissues like the heart blood vessels things of that nature
four 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 gonna 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 sawed
tissue and would be light gray okay so that's 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 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
puppet 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 gonna see two dimension on a
lateral film you'll be out actually make out three dimensions and you'll be able
to see things behind the heart for instance Whittle just pair 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 but a patient is sick laying in a bed you're
just gonna 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 gonna 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
an elective caesarean 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 systematic 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 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
add elective the right lung and the way you'd 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 Clavin holes 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're 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 fractures 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 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