B2 High-Intermediate US 50 Folder Collection
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welcome to another medcram lecture so I hear this question a lot how does the
corona virus actually kill people there's a recent article in The Lancet
that showed that of 41 people that were admitted to the hospital six of them
died and all of them were on ventilators and they died with something called a
RDS and a RDS is how the corona virus kills it's not just the corona virus but
many other viruses including the influenza virus that we have every year
how is it that this happens it's through acute respiratory distress syndrome and
I'm gonna explain to you how that happens so you first have to understand
lung Anatomy and to understand that I like to show you a tree so a tree has a
tree stump and then it branches and then those branches branch and then further
those branches branch until finally you get to the leaves and these leaves
capture the sun's rays and that's what gives you photosynthesis and that's how
the tree lives and so what happens is that this tree and the branches increase
the surface area of the leaves on the tree so that if you were to pluck off
all of the leaves and you were to put them on the ground next to each other
the surface area that is represented by those leaves would be larger than the
shadow that is produced by the Sun on that tree well it's the same exact thing
that happens with your lungs you've got an airway and then that airway divides
into a right mainstem bronchus and into a left mainstem bronchus and then you
have a right upper lobe you have a right middle lobe right lower lobe left upper
lobe and you have a left lower lobe so this is the left side this is the right
because you're looking at the patient and then these things of course divide
into much smaller branches and instead of leaves at the end of all of these
things what you have is something called an alveoli which is a tiny little small
grape like structure that the air gets into and the air of course has oxygen so
what does this look like on a large scale here's what an alveolus looks like
how many alveoli are there in the human body well there's
about 600 million of them these are very very small so what happens is
deoxygenated blood comes by and its job is to pick up the oxygen that comes in
to the alveoli and then when that oxygen comes in it oxygenates the blood and
then that blood goes back to the heart and then to the body and all your
muscles that's how you get oxygen and so you can imagine that this is very very
thin because the oxygen which comes down here has to diffuse into the bloodstream
so far so good but what happens well just like when you
hit your finger in the door your finger swells that's because there's
inflammation occurring where you hit your finger in the door and inflammation
causes a leakage of fluids into the tissue space so what happens here is
that you get a viral infection the virus affects your lungs and with a RDS the
entire lung becomes inflamed not just in one area like you would have with a
pneumonia
or one particular area for instance on your finger and it would just stay in
one particular finger in your whole hand wouldn't swell no with a RDS the entire
lung goes crazy with inflammation and so what happens air instead of having a
nice thin area inflammation goes everywhere and you get a large barrier a
fluid that goes into the interstitial space furthermore these capillaries
start to become leaky and fluid starts to leak into the alveolar space as well
and this starts to fill up with liquid proteinaceous liquid liquid that
prevents oxygen from getting into the bloodstream and so instead of having
nice oxygenated blood this blood becomes hypoxic and you become hypoxic if you
have a RDS and you have a hard time breathing and that's when you get placed
on the ventilator there's really nothing you can do to speed this up there's
nothing that you can do to slow it down you have to be supported on the
ventilator so that you're getting enough oxygen and that the Machine can breathe
for you until just like everything else after you hit your finger in the door
and the swelling goes away this fluid will eventually go away as well the key
though is keeping you supported during that period of time until the fluid goes
away and then once again the oxygen will be able to go back into the system and
you will get oxygen back to your tissues so here's another look at that we get
oxygen that's going down into these criminal structures called the alveoli
they go in to these alveoli and they cause deoxygenated blood to turn into
oxygenated blood and then go back to the heart so I'm going to show you three
things today that we have learned in the last 20 years that can improve survival
in these patients who are on ventilators to help them beat coronavirus or for
that matter any other virus whether it be influenza whether it be respiratory
syncytial virus any other kind of virus for beating and getting better if you
have a RDS and you're on the ventilator so the first thing that
look at is what they noticed back in 2000 and actually before is that when we
put people on the ventilator and the ventilator puts a breath into their
Airways what we were trying to do is we were trying to make sure that we were
ventilating patients well and that's important in some situations because the
blood that is poor in oxygen also has carbon dioxide which is given up from
the muscles well this carbon dioxide would need to
be ventilated to be taken out on exhalation so co2 would be coming out
well in order to do that we got to make sure that enough volume of air was going
back and forth back and forth the problem with that though is that we were
inflating these alveoli and then when we were releasing the pressure and letting
the air out these alveoli would collapse down and nothing was keeping them open
so they would be opening and closing opening and closing shutting and opening
and so that was causing a lot of shear stress and of course what's the whole
problem here that we've got inflammation is what's causing the whole problem here
in the first place and that's causing these membranes to become very thick and
the oxygen can't get in there and so by ventilating these patients with large
tidal volumes we were causing the inflammation to actually get worse than
it would have been if we hadn't done that and so the scientists started to
look at this and say wait a minute what happens if we just put a lot of
pressure down here to keep these alveoli open and only use a small amount of
tidal volume to ventilate these patients and yes we won't be able to get as much
carbon dioxide out of them but we don't really care so long as we're not adding
more inflammation to it and so that first thing that we looked at this is
back in the early 2000s that is came out is low tidal volume and that would
almost certainly cause the pco2 or the partial pressure of carbon dioxide in
the blood to go up so this was called a low tidal volume strategy and sure
enough paper was published in 2000 in the New England Journal of Medicine that
showed that we could affect change and we could decrease the mortality at
the time from 40 percent down to about 31 percent mortality so that was a huge
drop in mortality and all we did was we just ventilated people differently using
low tidal volume now when you're ventilating people with low tidal volume
it's not very comfortable they're trying to breathe more because they don't like
that increased carbon dioxide levels and so they would try to breathe over the
ventilator and it would try to breathe differently than what the ventilator was
telling them to do and in these cases we would usually sedate the patients but if
we sedated them too much bad things could happen to them they could get
blood clots their blood pressure would go down and so the second thing that
they came up with was actually paralyzing these patients using
medications so that they were in perfect sync with the ventilators and so that
was paralysis paralysis requires pretty intensive care in the intensive care
unit you need good ancillary services you need good respiratory therapists you
need good nursing something that you might not get if there's a huge outbreak
but you could get if attention was made to this so this paper also published in
the New England Journal of Medicine and by the way I'm gonna give links to all
of these papers in the description below they were able to drop the mortality
from 41 percent down to 32 percent and this paper was published in 2010 so far
so good what we also started to realize is that patients in the hospital for
whatever particular reason if you ever look at them in bed they're on their
back and what we decided to do was flip them over and there was a number of
reasons for this so that their belly was down and that their back was up we call
this prone positioning and if you do this for about 17 to 18 hours a day you
can actually decrease the mortality they found from 33 percent down to 16 percent
and this paper was published back in 2013 and so you can see here three
breakthroughs in treatment of a RDS the final common
pathway for morbidity and mortality in the coronavirus that we're talking about
but the other thing about this that's interesting is we can do a lot if we
catch it early and we get people into the hospital and we get them in the
intensive care unit and we get them on ventilators and we're able to
appropriately treat them with good quality medical care and three things
that really make a difference then we've got a good chance so that they're not
another statistic of mortality but they survive this and so really the purpose
of putting these updates on is to make sure that people understand the medical
background of what's going on sometimes these stories about how brakes can be
very scary and for good reason but we need to understand medically what
it is that's going on because knowledge is power if you have any other questions
about this please visit my site at make cram comm thanks for joining us
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How Coronavirus Kills: Acute Respiratory Distress Syndrome (ARDS) & Treatment

50 Folder Collection
Mia Chang published on February 25, 2020
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